Imágenes de páginas

both fossil and recent, with which we are acquainted. In doing this it has naturally occurred, that so:ne genera comprize merely such as are found in a recent state, some are solely composed of fossils, and others contain both fossil and recent species.

His two grand divisions depend upon the structure of the animal inhabiting the shell, the first comprizing such as have a distinct head, the second those in which this part is not disa tinguishable from the mass of the animal. It is by no means necessary, however, to be in possession of the inhabitant in order to determine to which division a shell belongs. Indeed, with respect to the fossil species this is never possible, and with many of the others it has only been inferred, that such is the formation of the animal, from apalogy. The cephalous shells are all univalyes, with the exception of the sirgle genus Chiton ; the acephalous are bivalves, or inultivalves. Mr. P. enumerates ninety-one genera of the former, and sixty-nine of the latter, several of which, however, are not known to afford fossil' species. A very great proportion of the mineralized shells, with which we are acquainted, have been found in the neighbourhood of Paris, and in the corresponding strata in this country. The former, which are in the most exquisite preservation, have supplied Lamark with a considerable part of his materials; and the latter have been already illustrated with considerable ability by Solander, in Brander's Fossilia Hantoniensia; but there is scarcely a limestone or (chalk stratum which does not afford a greater or less abundance. Among the most curious in every respect, must be reckoned the multilocular univalves, comprising the genera Nautilus, Spirula, Orthocera, Hippurites, Belemnites, Ammonites, Baculites, Hamites, &c. Some of these preserve the nacre, or mother of-pearl, with all its native brilliancy, as in the fire-marble of Carinthia, which even exceeds the opal in the vivid Aashes of colour which it reflects. Others are so completely mineralized, that their remains can only be faintly traced on the polished surface of the marble in which they are imbedded. Some appear to have an indefinable n'ultitude of spirai convolutions; while others seem to have been transformed from a spiral into a tubular form; and others again consist of a strait tube ending in a spiral extremity.

The chambers into which these shells are divided, the least of which was probably occupied by the animal, while the remainder served as a pireumatic apparatus, by means of which it could alter its specific gravity, so as to rise from the deepest abysses of the sea to the surface, and descend at pleasure,) are separated, in Nautilus, &c. by simple divisions, but in Am. monites, &c. the edges of these divisions are waveu, so as to produce on the cast of the shell an appearance of tracery ini. mitable by art. The recent species of Ammonites, if indeed they can strictly be referred to this genus, are so small as to require the aid of the microscope to examine then); while several of the fossi] species exceed the size of a cart wheel, and are so diversified in forın, that Rosinus believed that he had distinguished three hundred species. And as the process of mineralization seldom leaves a trace of the colour, which in recent shells must frequently be allowed to constitute a difference of species, and as the number of strata which contain these relics are but partially examined, it is more than probable that we are acquainted with a small portion only of what once existed.

The genus Nummulites is remarkable, not only on account of the singularity of its internal configuration, which is extremely intricate, but from the abundance in wbich it occurs in the fragments surrounding the Pyramids of Ghize, as noticed distinctly by Strabo,* who mentions the tradition prevalent at his time, that they were the petrified remains of the pulse on which the workmen subsisted. Mr. P. mentions the fossil as known to Pliny, but omits this babitat.

Lamark makes no mention of any species of Mya being found in a fossil state; and Mr. P. seems doubtful as to the specimens which he wishes to refer to this genus. Many of the Myæ being fresh water shells, it is evident they may be sought for in strata which appear to have been formed by its agency, as the coal strata, abounding in the remains of

vegetables, and we are much mistaken if two or three distinct

species are not tolerably abundant in the ironstone which constantiy attends this formation. Indeed the masses of calcareous earth, and the veins of calcareous spar intersecting the nodules of ironstone, appear to owe their origin to decomposed: shells of this genus.

We must regret that Mr. P. in this part of his work is so much absorbed in the natural history of his subjects, as frequently to neglect their geological relations. It is true, thai few col. lections of petrifactions having been formed with the express, view to illustrate geology, the information attached to the re. spective specimens is seldom satisfactory in this respect; but where little is known on an important subject, it behoves the lover of science to communicate all that he can ; and Mr. P. might certainly have contributed more than he has done.

Our author is also inuch too concise in his account of fossil FISHES, of which such an astonishing variety has been found in the mountain of Vestena Nuova, or Monte Bolca, and in

* Geogr. Lib. XVIJ.

the quarries of Pappenheim and Eningen; nor does he figure a single specimen, either British or foreign, though indigenous specimens, well deserving being thus commemorated, must have been accessible to him. We expre-s our disappointment at this onnissjon, because we strongly suspect that the numerous species, reported to be identical with such as exist at present, will, upon minute investigation, be found in some degree to differ. It however deserves notice, that the greater part of the supposed recent analogges of both fossil shells and and fossil fishes are inhabitants of the tropical seas. This observation cannot be ascribed to an imperfect knowledge of these species, which might leave sufficient latitude for the imagination to suit them to the fossils as occasion required; the Indian shells and fishes, being sufficiently common in our cabinets to allow of minute investigation. If, however, with respect to animals, it may be looked upon as an ascertained fact, that our regions were once occupied by a race of beings resembling those which are at present confined between the tropics; we might be tempted to suppose, that the vegetables also bore a resemblance to those of the torrid zone. But this is by no means proved by their fossil remains; first, because the supposed analogy which has been traced in some, as in the so called Euphorbia, Arundines, &c. is extremely superficial; and, secondly, because we have no sufficient evidence that the strata containing fossil shells, fossil fishes, and fossil vegetables, were formed at the same, or nearly the same period, except in the case mentioned by M. Faujas at Rochesauve, where the remains of fishes are said to be found among the impressions of the leaves of plants. But we are the more inclined to suspect that this circumstance requires closer examination, notwithstanding the celebrity of the reporter, as he asserts, that many of the leaves were those of trees and plants indigenous to the south of France.

Though the remains of entire fishes are rare in this country, we are pretty well provided with fossil teeth, palates, vertebræ, &c. which form a conspicuous part of every collection. The enormous size of some of them, particularly Maltese specimens, is truly astonishing. Lamark calculates that a shark's tooth, in the National Museum in Paris, must have belonged to an animal not less than seventy feet in length; yet this specimen is not the largest known. Their close resemblance to the teeth of existing species, warrants the supposition that their proportion to the size of the animal did not differ very widely from that which subsists in their allied species.

The ENTOMOLITHI, or mineralized remains of insects, are but few in number; and of these but one species, the so called Dudley fossil, occurs in any abundance. We are inclined to think that Mr. P. errs in ascribing to the original the power of covering and uncovering its eyes;, the reticulated cornea of insects, in general, by no means requiring such a defence. It must also be owing to a mistake that the supposed Helmintholithi are introduced into the middle of this section, to which they cannot belong.

In treating of the AMPHIBIOLITII, Mr. P. has availed himself of the labours of Cuvier, and Faujas St. Fond. The tortoise and crocodile are the only known genera, species of which exist in a fossil state. Of the former, specimens, but gene. rally in a mutilated condition, occur in the island of Shepy, and fragments on the banks of the Severn. Some have likewise been found in the excavations on Highgate-bill. With respect to their recent analogues he remarks : “ It appears that of fourteen fossil tortoises one only appears to be of a known species, and that of the remaining thirteen none can be referred to any known species, but five of them are decidedly of new species.'

The investigation of the different species of crocodiles is al. most entirely borrowed from Cuvier, and leads to an account of the celebrated Maestricht animul, first scientifically described by Mr. P. Camper in the Philosophical Transactions. It appears to resemble the Monitor in many respects; but instead of being a feeble animal two or three feet in length, to have attained to the size of the crocodile, and, from the attendant marine productions, to have inhabited the ocean.

The fossil remains of BIRDS (Ornitholithi) are still rarer than those of insects; and so many pretended specimens have been proved to belong to animals of a different class, that their existence has been almost questioned. It is, however, indubitably ascertained, that the bones of birds are occasionally found in a mineralized state; and Mr. Cuvier concludes, that the quarries in the vicinity of Paris furnish those of five or six distinct species.

Mr. P. prefaces the remaining part of his work with the following candid acknowledgment.

Having now to commence the examination of the fossil remains of those animals which are comprised in the Linnean class MAMMALIA, I feel that it

may be necessary to endeavour to satisfy you with respect to the manner in which this part of my task is accomplished. I fear that you will, at first, experience feelings of disappointmen, on my avowing to you, that the following pages will almost entirely be employed in placing before you the discoveries which have been made by another; and you will probably imagine that this acknowledgement can hardly be made with out occasioning me to experience some degree of mortification. But the truth is, that knowing, that as you proceed you must be highly pleased, I am thoroughly satisfied with merely recounting to you the most prominent

particulars of those important discoveries, which have rewarded the patient and unabating exertions of Cuvier.'--To have admitted less of the discoveries of Cuvier, in the present work, would have been unjust to those many who cannot obtain the voluminous, expensive, and almost prohibited works, in which they are contained. To have introduced less would indeed have been to have sparingly employed the only light almost which has ever been thrown on this most interesting subject.' pp. 307, 308.

We do not regret the plan which Mr P. has pursued, as he has given us a very judicious and valuable abstract of the papers alluded to; but we fear that, in many parts, he adheres to his author's researches in comparative anatomy too closely to be intelligible to many of his readers, who would be satisfied with the results. Mr. P., as well as Cuvier, follows Dumeril in the arrangement of this part of his work. Of the families ceti and amphibia few fossil specimens have been discovered. In the family solipedes, the teeth of a species of horse are found in great quantities, in some parts of France and Germany, mixed with those of the elephant, which proves that the animal existed along with the elephant on our continent; but whether the species was the same with any now existing, cannot be ascertained.

The most remarkable fossils of the family ruminantia, are the enormous stag's horns found in Ireland, which appear to have belonged to an animal now extinct; but the horns and bones of other species have also been found, differing, in gee neral, less from those of the present tenants of our globe than the mineralized remains of mammalia are usually found to do. They form the greater part of those immense concretions of bones in the fissures of the rock of Gibraltar, in the island of Cergio, and other places, which have been long supposed to contain the relics of the antediluvian race of man, but which are now proved to possess not a particle of human bone.

After menționing the remains of the elephant, which are tolerably abundant in several places, Mr. P. devotes an entire letter to the consideration of the Mastodon, of which Cuvier has discriminated several species. Respecting the celebrated Mastodon of the Ohio, he concludes that it

did not surpass the elephant in height, but was a little longer in proportion; its limbs rather thicker; and its belly smaller. It seems to have very much resembled the elephant in its tusks, and indeed in the whole of its osteology; and it also appears to have had a trunk. But notwithstanding its resemblance to the elephant in so many particulars, the form and structure of the grinders are sufficiently different from those of the elephant, to demand its being placed in a distinct genus. From the later discoveries respecting this animal, he is also inclined to suppose that its food must have been similar to that of the hippopotamus and the boar, but preferring the roots and fleshy parts of vegetables ; in the search of which

« AnteriorContinuar »