A Monograph of the Trilobites of North America: With Coloured Models of the Species

Part 1

Transcriber Note: Text emphasis denoted as Italics.

A MONOGRAPH OF THE TRILOBITES OF NORTH AMERICA: WITH Coloured Models of the Species.

Multa renacentur quæ jam cecidere.--Hor.

JACOB GREEN, M. D. Professor of Chemistry in Jefferson Medical College.

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PHILADELPHIA:

Published by Joseph Brano, No. 12, Castle Street.

Clark & Raser, Printers.

1832.

Entered according to the Act of Congress, in the year 1832, by Joseph Brano, in the Clerk's Office of the District Court of the Eastern District of Pennsylvania.

To JOHN GEORGE CHILDREN, Esquire, F. R. S. L. & E.

The kindness which a traveller receives when in a distant land, must ever be among his most pleasing recollections your attentions therefore to me, during any short residence in London a few years since, cannot easily be forgotten. Suffer me, then, to inscribe this little work to you as a token of my gratitude.

Our pursuits in the Natural and Physical Sciences have been congenial. Your interesting researches with your original and magnificent Galvanic Battery, first drew my attention to the calorific effects of that mysterious agent; and your works on Natural History have stimulated my exertions in the same fascinating pursuit.

A large portion of your time and fortune have been devoted to the patronage or the cultivation of Natural Science so that the dedication of this work to you, if it were infinitely more worthy of your acceptance, would be due from me, both as a tribute of high respect, as well as of grateful acknowledgment.

Philadelphia, October 1st, 1832.

EXPLANATION OF THE PLATE.

Figure 1. Trimerus Delphinocephalus. 2. Calymene Diops. 3. Asaphus Micrurus. 4. Cryptolithus Tessellatus. 5. Paradoxides Boltoni. 6. Triarthrus Beckii. 7. Isotelus Cyclops. 8. Dipleura Dekayi. 9. Head of D. Dekayi. 10. Ceraurus Pleurexanthemus.

The above figures represented on the Frontispiece to this volume, were first published in the Monthly Journal of Geology, &c. for June, 1832, and I am indebted to C. A. Poulson, Esq., for the use of them in this Monograph.

INTRODUCTION. —————

Some geologists 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. We propose not to enter the field of 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.

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 term Trilobite has 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 the horse foot or king crab (limulus polyphemus), so common on our sea coast. The middle portion is the abdomen, 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 the tail, 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 the front, or forehead; and the lateral portions the cheeks. 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 these petrifactions 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. 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.

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.

Part 2

The Trilobite is supposed by many naturalists to be one of the first animated beings of our earth called into existence by the great Author of nature. 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, the Dudley fossil. Linné gave it the name of the Paradoxical insect; but whether an insect, a crustaceous animal, or a shell, is still considered by many as problematical.

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. Until that period, the term Entomolithus 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.

Our object in the present undertaking being merely to give a monograph of the species of Trilobites found 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 of species has been sufficiently advanced to furnish us with numerous and well authenticated facts."

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