INTRODUCTION.

Somegeologists imagine that the order of creation is registered in the rocks which compose the external crust of the earth, and that they can there clearly read a progressive development of organic life; in other words, that a succession of more perfect animals may be traced in ascending from the lower strata to the upper or more recent formations; that there is a gradual approach to the present system of things, and a succession of destructions and creations; worlds of living beings alternating with worlds of desolation and death, antecedent to the existence of man.

Others, again, contend that there is often a wide and palpable discrepancy between the nature of the rock, and the fossils which it contains, and, therefore, that such inquiries afford no clue, whatever, to the order of creation.[1]We propose not to enter the fieldof controversy. Fossils are undoubtedly historic medallions of remote periods in the natural history of our earth, and our design is, merely to illustrate with them a neglected department of ancient zoology, by describing a few which have recently fallen under our own observation.

[1]Nothing can be more opposed to true science, than to pronounce on the priority of formation, or the comparative age of rocks, from either their structure, or the organic remains they present. M. Alexandre Brongniart thus propounds his opinion: "In those cases where characters derived from the nature of the rocks are opposed to those which we derive from organic remains, I should give the preponderance to the latter." This seems to us to imply an admission, that nothing definite can be inferred from thenature of the rocks; moreover, that between the nature of the rock, and the organic remains, there may be a palpable discrepancy; and that these may be even at complete antipodes with each other. The event has proved, from what we have already mentioned, that no evidence as to priority can be obtained from the nature of the fossil remains displayed in particular strata. In addition to what has been said on this subject, we may further state, thatencrinites,entrochites, andpentacrinitesare found in clay slate, grauwacke, transition limestone, alpine limestone, lias, muschelkalk, and chalk. It may be reasonably asked how these three species of fossils could indicate any particular formation, when they are found in so many types and structures of rocks altogether different? If they would go to prove any thing at all, it would be that of acontemporaneousformation; but certainly not distinct epochas.See Eclectic Review, July, 1832.

In some varieties of rocks there is often found the fossil remains of an animal which bears some resemblance to certain species of the crab. The back of this organic relic is commonly divided by two deep grooves or furrows, into three longitudinal lobes, and from this circumstance, the termTrilobitehas been applied as a family name to distinguish this whole race of beings. This general appellation, however, though in most of the species, highly appropriate, is by no means applicable to all.

The individuals which compose the family of the trilobites resemble each other in many important particulars,and form together an exceedingly natural group. The body, with but few exceptions, is divided transversely into three parts. The anterior portion or head often resembles the buckler of thehorse footorking crab(limulus polyphemus), so common on our sea coast. The middle portion is theabdomen, and is always separated transversely into a number of segments or articulations, generally diminishing in breadth as they recede from the head. The posterior end is thetail, which, though in some species, a mere prolongation of the abdomen, that can scarcely be distinguished from it, yet in others it assumes a genuine caudal appendage.

The head of the trilobite is also generally divided into three parts: the middle is called thefront, or forehead; and the lateral portions thecheeks. In most cases, a projecting tubercle, or knob, is observable on the anterior surface of each cheek, which has much the appearance of an eye. Its reticulated structure is in many instances so analogous to that of the eyes of some crustaceous animals, and also of some species of insects, that there can be but little doubt that these tubercular projections, were true organs of vision.

Some of the genera which belong to this remarkable race of fossil animals, possessed the power of rolling or coiling themselves up into a kind of ball, like certain species of insects, or like the armadillo; and they are always found embedded in the rocks in this attitude.

Such are the general characters by which thesepetrifactions may be known, and they will be found illustrated in a manner more or less striking, in most of the species. The exceptions, which rarely occur, will be distinctly marked, when the species are described.

The superior covering, or upper shell of the trilobite is the only part of the animal, concerning which we have any satisfactory knowledge. It is conjectured that it was furnished with articulated feet, but no traces of any organs of progressive motion have hitherto been fairly discovered.[2]Hence, it may be reasonably supposed, that the structure of the lower portions of the animal were so soft and delicate, as to render them incapable of sustaining the process of mineralization, which the hard crustaceous covering of the back so successfully undergoes.

[2]Mr. Parkinson states, that in a trilobite which he possessed he thought he perceived thepointsof the feet; but on endeavouring to detach the piece of rock in which it was embedded, the specimen was entirely shivered, though he worked at it with the utmost care. A portion of the underside of a trilobite (Isotelus gigas) near the anterior edge of the head, was distinctly ascertained, by Dr. Dekay, but only enough to convince him of its analogy in this part with that of the limulus polyphemus no organs of locomotion could be seen. Mr. Stokes, the distinguished fossilist of London, has confirmed the observation of Dr. Dekay, by some dissections of his own.

That these petrifactions were once marine animals there can be little doubt, for they are always found associated in the same rocks with shells, and other productions peculiar to the sea.

The Trilobite is supposed by many naturalists tobe one of the first animated beings of our earth called into existence by the great Author of nature.[3]It was first noticed more than two centuries ago, among the petrifactions which abound in a calcareous rock, at Dudley, in England, and was from this circumstance, called for a long time, theDudley fossil. Linné gave it the name of theParadoxical insect; but whether an insect, a crustaceous animal, or a shell, is still considered by many as problematical.

[3]It is obvious, that if most of the gelatinous animals which now inhabit our seas, were to become extinct, few or no traces of them could be found in any succeeding depositions of earthy matter. Whatever kind of animal life, therefore, may have been the first which appeared in our planet, must be entirely hypothetical. All that we can with certainty say of it, is, that it was best adapted to the circumstances, in which it was to exist, and that it was consistent with the wisdom and design which we see every where pervading the universe.

Notwithstanding the high antiquity of the family of the Trilobites, and the remarkable characters the different individuals which compose it, sustain in the animal kingdom; till within a very few years, the whole race has been almost entirely neglected by naturalists. The first attempt at any systematic arrangement of the genera and species, was made in 1815, by Alexander Brongniart, Professor of Mineralogy, &c. &c., in Paris.[4]Until that period, the termEntomolithus Paradoxus, proposed by Linné, was applied to all the fossil remains, which in their general appearance bore any resemblance to that found at Dudley, and which he first described under that name. The confusion, therefore, which existed in this department of natural science, may readily be imagined; especially, as the species rapidly multiplied, when they were supposed to throw some rays of light on certain obscure geological phenomena. Soon after the appearance of Professor Brongniart's excellent work, the attention of other naturalists was directed to this neglected part of creation. The most important memoir, on account of the number of species, well figured and described in it, is one by Dr. E. W. Dalmann, published in the Transactions of the Swedish Academy, for 1826. There is also in the Acts of the Royal Society, at Upsal, an excellent paper on this subject by Professor Wahlenberg. Our highly esteemed friend, Dr. James E. Dekay, has also given in the first volume of the Annals of the Lyceum of Natural History of New York, some very interesting and ingenious observations on the nature and the structure of the Trilobites, with a description of a new genus. These are the principal authorities which have been consulted in arranging the present work.

[4]I cannot let this opportunity pass, without acknowledging my obligations to Professor Brongniart, for his civilities, when on a late visit to Paris. Every one whose curiosity leads him to examine the royal manufactory of porcelain, at Sevres, of which he is the director, will no doubt acknowledge that his talents as a philosopher, are rivalled by his accomplishments as a gentleman.

Our object in the present undertaking being merely to give a monograph of the species of Trilobitesfound in the rocks of North America; we leave to other and abler hands the more difficult and interesting task of determining with precision the connexion which may exist between these organic reliques, and the relative ages of the strata in which they are found.

It is supposed, indeed, that a sufficient number of well characterized species have not yet been collected and accurately described, to throw any certain and clear light on otherwise doubtful geological phenomena. What has been remarked by De Candolle, with regard to botanical geography, is perhaps true of these fossils as to solving the difficult problems of geology—"Let us not forget," says he, "that this science can only be commenced when the study ofspecieshas been sufficiently advanced to furnish us with numerous and well authenticated facts."

We are well aware of the difficulty of settling the line which ought to divide species. Individuals perfectly identical in all their parts, are rarely, if ever seen; though a general resemblance may be easily traced. Among fossils, just discriminations of this kind are more delicate, than in recent specimens. The hand of time, accidental causes, and the influence of atmospheric changes often produce such characters as to render the determination of fossil species an exceedingly difficult task. We have no doubt, therefore, that a few of our Trilobites, which are now considered as perfectly identical with some found in Europe, will upon fuller examination, be discovered to be dissimilar, and of course certaingeological speculations grounded on the first opinion, be ultimately abandoned.

The geographical distribution of organic remains, is an exceedingly curious inquiry. If accurately pursued, without reference to any preconceived theory, it will no doubt furnish much information as to the comparative ages of the different strata which compose the external crust of our planet—for that these strata were deposited or formed at periods of time more or less remote from each other, every one knows, to be a generally admittedgeological fact. The occurrence of similar fossils in districts of country remotely situated from each other, certainly presents a phenomenon highly interesting to the speculative naturalist, and apparently indicates that the same powerful and general causes must have concurred to produce these isomorphous depositions. No fossils have contributed more to this kind of information, than those of shells, and as the mineralized species could not be satisfactorily studied, except by accurately comparing them with those which now inhabit our seas and continents; the search for shells, has become, from a simple amusement, the study of scientific men—or, as a writer remarks, "it was only after the period when it was perceived that geology and ancient zoology were destined to be enlightened by their fossil remains, that this research passed from the hands of amateurs into those of naturalists."[5]

[5]We have not unfrequently noticed, both in the writings and conversation of some geologists, a disposition to sneer at the subsidiary branches of natural history. Mineralogy and conchology, are light and mean in their estimation, when compared with the study of extensive strata and ponderous boulders. Like Irving's testy governor of Manahatta, who settled the accounts of his clients by placing their books in the opposite scales of a balance, they decide on the value of a science, by the absolute weight of the objects embraced by it. Geology, as well as any other branch of natural history, may degenerate into a mere love for the curious, or have for its principal aim, the perfection or improvement of some ideal system of classification, without advancing a single step further.

Another curiousgeological factappears to be established more especially by fossil trilobites; it is that precisely the same species of animal relic, is the most generally diffused over the globe, in proportion to the antiquity of the rock which contains it. Thus the transition limestone of England, France, Germany and Sweden, contains the species called the Calymene of Blumenbach, in common with the same formation which extends over so large a portion of the United States.

Different genera and species of the trilobite are now found in almost every part of the globe, and are frequently exceedingly abundant in the rocks which contain them. That they must have swarmed in particular places, is abundantly evident from a number of localities in our own country,—millions, for example, must have lived and died not far from Trenton falls, in the State of New York. There are very few of the numerous visiters to that romantic cascade, whose curiosity is not awaked, by the multitude of these petrified beings, seemingly of another world, which are there entombed.

Although many parts of the trilobite are now found distributed through the rocks which contain them, in such a manner as to lead to the conclusion, that they were separated by decomposition, after the death of the animal; yet the perfect preservation of others, and the rolled and disjointed attitudes which we should expect such creatures to assume when disturbed, lead to the conjecture, that they have been often suddenly destroyed, and as suddenly enveloped in that earthy matter, which afterwards became an indurated rock; thus preventing the separation of the harder parts, by the slow process of decomposition.[6]

[6]Vide De la Beche's Geological Manual.

The fossil remains of the trilobite family, are supposed by most naturalists to belong to a race of beings now extinct; but from the strong analogy which exists between them and certain species of crustaceous animals now living, it is highly probable that they will yet be found alive. This opinion will not be regarded as visionary, when it is recollected how large a portion of the surface of the earth is still unexplored by its enlightened and civilized inhabitants—how small the number of animated beings are yet known to the scientific world—and above all the fact, that many animals as confidently declared to be peculiar to a former world, are now found to be among the creatures at present in existence. This opinion, we think, is quite as plausible, and far more interesting, than the blank and unsatisfactory hypothesis thatall the trilobites are confined to an order of things before the present glorious creation.[7]

[7]The incorrectness of the inference that all the genera and species of fossil animals found in the transition rocks must be now extinct, will appear from the following extract from Bakewell's Geology:—"TheMadrepora stylina, so common in transition lime-stone rock, is entirely wanting in the secondary and tertiary strata, but a living animal of this species has been recently discovered in the South Seas. The Pentacrinus makes its first distinct appearance in the lias; but is not frequently met with in the upper strata, and disappears entirely in the uppermost formations: hence it was long supposed that the species was extinct. A living Pentacrinus has recently been discovered in the West Indies, and its stem and branches in a perfect state have been sent to this country." (England.) In the Museum at Albany, N. Y., I have examined a recent Pentacrinus, which I conclude, came from the West Indies, from the proprietor's account of the manner in which he obtained it. It has been a very perfect specimen but the branches are gradually dropping off.

There appears to have been known to naturalists, when the improved edition of Prof. Brongniart's work on the trilobites appeared in 1822, but 17 well marked species, and out of which he constructed the five following genera, which he thus characterizes.

Bodycapable of contraction into nearly a semicylindrical sphere.

Bucklerwith many tubercles or folds. Two reticulated eye-shaped tubercles.

Abdomen and Post-abdomenwith entire edges. Abdomen divided by 12 or 14 articulations.

No elongated tail.

Bodybroad and rather flat. Middle lobe prominent and very distinct.

Flanks or lateral lobeseach double the size of the middle lobe.

Submembranaceous expansionsextending beyond the lateral lobes.

Bucklersemicircular, with two reticulated eye-shaped tubercles.

Abdomendivided into 8 or 12 articulations.

Bodymuch depressed into an oblong ellipsis not contractile into a sphere.

Buckleredged, a slight longitudinal furrow arising from its anterior extremity. Posterior angles elongated into points.

Without any tuberclesexcept the eyes, which are neither prominent nor reticulated.

Longitudinal lobesslightly prominent.

Abdomenwith 8 articulations.

Bodydepressed not contractile.

Flanksmuch broader than the middle lobe.

Bucklernearly semicircular three transverse furrows on the middle lobe.

Eye-shaped tuberclesnone.

Abdomenwith 12 articulations.

Archesof the lateral lobes, more or less prolonged beyond the membrane which sustains them.

Bodyellipsoidal—semicylindrical.

Buckler and flanksedged—the edges being slightly elevated.

Middle lobewith two transverse divisions, each composed of a single piece.

Two glandulartubercles on the anterior part of the body.

In 1824, Dr. J. E. Dekay added a sixth genus to the family of the trilobites, which he describes in the following manner.

Bodyoval oblong, often contracted, not unfrequently extended.

Headorbucklerlarge and rounded, equalling the tail in size, with but two oculiform tubercles.

Abdomenwith 8 articulations.

Frontal process beneath, with two semilunar terminations.

Post-abdomenortailbroad, expanded with indistinct divisions, as large as the buckler.

Longitudinallobes very distinct.

This genus, he remarks, will be sufficiently distinguished from the five genera proposed byM. Alexandre Brongniartin his valuable and truly philosophical work on the trilobites by the following particulars.

FromCalymene. By the presence of but two tubercleson the buckler not reticulated; by the abdomen with but 8 articulations.

FromAsaphus. By the middle lobe, which is double the size of the lateral ones; by the absence of a membranaceous expansion on the sides; by the non-reticulation of the eyes, &c.

FromOgygia. By the rolled form, the rounded posterior angles of the buckler, and the distinct articulation of the longitudinal lobes.

FromParadoxideandAgnosteby characters too obvious to be enumerated. (See Annals of N. York Lyceum, Sec. Vol. I. pp. 174-5.)

In 1826, J. W. Dalman published in the Transactions of the Swedish Academy, and also in a separate work, an account of the trilobites found in the North of Europe, in which he has enriched the family by a number of fine species, and with the following genera, which he modestly proposes merely as subdivisions.

Bodyshort, capable of contraction into a sphere, smooth, convex.

Abdomenwith about 8 articulations, without any dorsal longitudinal furrows.

Bucklersub-lunate, with large lateral eyes.

Tailexpanded, not so large as the buckler, without lobes.

Genus Eighth.Illænus.

Bodyovate oblong, contractile.

Headrounded in front, eyes small, in the temples, very remote.

Abdomenwith from 9 to 10 articulations, trilobate.

Tailexpanded as large as the head.[8]

[8]Some of the species described by Professor Dalman as included in this genus, we think ought to be referred to that of the Isotelus.

Bodyvery short, contractile.

Bucklerlarge, triangular, gibbous; eyes not remarkable.

Abdomenshort, articulations few (6?), trilobate.

Tailexpanded, not so large as the head.

Professor Dalman has two other genera, which he calls Olenus and Battus, the first is the Paradoxides, and the second the Agnostus of Brongniart.

In the 8th Volume of Annales des Sciences Naturelles there is a highly valuable paper "Sur les Trilobites et leurs gisemens," by the Count Rasoumowsky, in which he describes some new trilobites from Russia; the one which he has figured and described as a Calymene[9]from Tzarsko-Selo, undoubtedly belongs to a new genus, very near to the Isotelus. The middle lobe is visible or naked through its whole extent, and the lateral lobes near the tail are covered with a thick cuticular membrane. This genus we propose to call Hemicrupturus, and may be thus characterized.

[9]The editors of the Annales remark that this is not a Calymene, but that it appears to belong to the genus Asaphus.

[10]From three Greek words which signifyhalf-concealed tail.

Bodycontractile.

Buckleroculiferous and not lobate.

Abdomentrilobate, with 8 articulations.

Tail, costal arches covered, middle lobe naked.

The Asaphus expansus of Dalman, and several other known species may be arranged under this genus.

As Count Rasoumowsky has given no specific appellation to the fossil above alluded to, we propose to call it after his own name,Hemicrupturus Rasoumowskii. We examined the fine specimen from which our cast is taken in the cabinet of the Baltimore College, and for this favour we are indebted to the kindness of Dr. J. J. Cohen, one of the Professors in that rising institution.

The following list includesallthe genera and species of the Trilobite Family, hitherto described as far as known to the author. It is taken from De La Beche's Manual of Geology.

From the short descriptions given by Professor Rafinesque of the five last mentioned fossils, I conclude that they belong to the genus Calymene of Brongniart.

The study of the trilobites naturally leads to the consideration of those beings which appear to have inhabited our earth previous to the creation of man. Every one knows that the sceptical naturalist has drawn from these vestiges of organic life, an argument contradictory to the Mosaic account of the history of the world, and though every cavil of the least importance, urged against the truth of the sacred historian, has been triumphantly confuted, still, the geological sciolist boldly impugns his veracity, whenever any new facts in his science can be distorted tohis purpose. Such being the case, we cannot conclude this preface without briefly stating two or three methods by which any seeming discrepancies may be explained. First, those who imagine that the six periods of creation, mentioned in the beginning of the pentateuch, mean literally days of 24 hours each, believe that, as only a small part of the earth was at first required for the abode of man and the higher animals, the present continents might have remained as long beneath the waters, and have undergone every change necessary to solve this geological puzzle.

Again, others have thought that Moses, after recording, in the first sentence of Genesis, the great truth that all things were made by the will of an intelligent Creator—passed silently over some intermediate state of the earth, which had no direct relation to the history, or to the duties of man—and proceeded to describe the successive appearance of the present order of things. On this supposition, the fossil remains and peculiarities in the structure of the earth may have belonged to that intermediate state.

A third method of explaining the difficulty, and which we think highly satisfactory, is, by understanding the days of creation to mean, not ordinary days, butperiods of time, in which the recorded events took place in the order described so briefly by the sacred historian. It is acknowledged by every one competent to judge, that among the Hebrews,daysandweekswere often used in this manner. The accordance between the order in which, according tothe account of Moses, the work of creation was accomplished, and the order in which the fossil remains of plants and animals are deposited in the earth, has surprised, and has been acknowledged by learned sceptics themselves.[11]

[11]The Baron Cuvier, on this subject, remarks, respecting the Jewish legislator—"His books show us, that he had very perfect ideas respecting several of the highest questions of natural philosophy. His cosmogony, especially, considered purely in a scientific point of view, is extremely remarkable, inasmuch as the order which it assigns to the different epochs of creation, is precisely the same as that which has been deduced from geological considerations."

It will be useless to push these arguments further. The catastrophes which have produced the secondary strata, and the diluvian depositions, could not have been local or partial phenomena; but rather than call upon a comet, with the abstracted philosopher, to deluge the earth for every new geological epoch—or to change the axis of motion of our planet—or to resort to any of his wild, fanciful, and impious theories, we should, with Sir Humphrey Davy, even prefer the dream that all the secondary strata werecreated, filled with the remains, as it were, of animal life, to confound the speculations of our geological reasoners.

Back to Index Next