Imágenes de página
PDF

mated nature, and place these extinct genera in close connexion with the living orders of Mammalia.

We may estimate the number of the animals collected in the gypsum of Mont Martre, from the fact, stated by Cuvier, that scarcely a block is taken from these quarries which does not disclose some fragment of a fossil skeleton. Millions of such bones, he adds, must have been destroyed, before attention was directed to the subject.

The subjoined list of fossil animals found in the gypsum quarries of the neighbourhood of Paris, affords important information as to the population of this first lacustrine portion of the tertiary series.* (See PI. 1. Figs. 73 to 96.)

* List Op Vertebral Animals Found In The Gypsum Of The Basin
Of Paris.

Pachydermata.

. Extinct species, of extinct genera.

'Palaeotherium ....
Anoplotherium ....
Cheropotamus ....

Adapts

r Bat.

Marsvpialia .
Rodentia . . .

Birds

Reptiles ...

Carnivora . .<

Fishes ...
VOL. I.-

I" Large Wolf, differing from any exist-
Canis . . -i ing species.

(.Fox.
Coatis (Nasua, Storr,) large Coati, now native of

the warm parts of America.
Racoon (Procyon, Storr,) North America.
Genette (Genetta, Cuv., Viverra Genetta, Linn.,)
now extending from the South of Europe to
Cape of Good Hope.
Opossum, small (Didelphis, Linn.,) allied to the

Opossum of North and South America.
Dormouse (Myoxus, 6m.,) two small species.
Squirrel (Sciurus.)

- Birds, nine or ten species, referable to the fol-
lowing genera: Buzzard, Owl, Quail, Wood-
cock, Sea-Lark (Tringa,) Curlew, and Peli-
can.
Fresh-water Tortoises, Trionyx, Emys.
Crocodile.

Seven extinct species of extinct Genera. Agast.

&

n o

I

-o

I

Besides the many extinct species, and existing genera of Mammalia that are enumerated in this list, the occurrence of nine or ten extinct species of fossil Birds in the Eocene period of the tertiary series, forms a striking phenomenon in the history of organic remains.*

In this small number of species, we have seven genera; and these afford examples of four, out of the six great Orders into which the existing Class of Birds is divided, viz. Accipitres, Gallinaceae, Gralte, and Palmipedes. Even the eggs of aquatic birds have been preserved in the lacustrine formations of Cournon, in Auvergne.f

It appears that the animal kingdom was thus early established, on the same general principles that now prevail; not only did the four present Classes of Vertebrata exist; and among Mammalia, the Orders Pachydermata, Carnivora, Rodentia, and Marsupialia; but many of the genera also, into which living families are distributed, were associated together, in the same system of adaptations and relations, which they hold to each other in the actual creation. The Pachydermata and Rodentia were kept in check by the Carnivora—the Gallinaceous birds were controlled by the Accipitres.

* The only remains of Birds yet noticed in strata of the Secondary series are the bones of some Wader, larger than a common Heron, found by Mr. Mantell in the fresh-water formation of Tilgate Forest. The bones at Stonesfield, once supposed to be derived from Birds, are now referred to Pterodactyles. A discovery has recently been made in America by Professor Hitchcock, of the footsteps of Birds in the New Red sandstone of the valley of the Connecticut, which he refers to at least seven species, all apparently Waders, having very long legs, and of various dimensions from the size of a Snipe, to twice the size of an Ostrich. (See PI. 26a. 26b.)

t In the same Eocene formation with these eggs, there occur also the remains of two species of Anoplotherium, a Lophiodon, an Anthracrolherium, a Hippopotamus, a ruminating animal, a Dog, a Martin, a Lagomys, a Rat, one or two Tortoises, a Crocodile, a Serpent or Lizard, and three or four species of Birds. These remains are dispersed singly, as if the animals from which they were derived had decomposed slowly and at different intervals, and thus fragments of their bodies had been lodged irregularly in various parts of the bottom of the ancient lake: these bones are sometimes broken, but never rolled.

"Le Itegne Animal, a ces epoques reculees, etait compose d'apres les tnemes lois; il comprenoit les memes classes, Jess memes families que de nos jours; et en effet, parmi les divers systemes sur l'origine des 4tres organises, il n'en est pas de moins vraisemblable que celui qui en fait naitre successivement les differens genres par des developpomens on des metamorphoses graduelles." (Cuvier, Oss. Foss. t. 3, p. 297.)

This numerical preponderance of Pachydermata, among the earliest fossil Mammalia, beyond the proportion they bear among existing quadrupeds, is a remarkable fact, much insisted on by Cuvier; because it supplies, from the relics of a former world, many intermediate forms which do not occur in the present distribution of that important Order. As the living genera of Pachydermata are more widely separated from one another, than those of any other Order of Mammalia, it is important to fill these vacant intervals with the fossil genera of a former state of the earth; thus supplying links that appeared deficient in the grand continuous chain which connects all past and present forms of organic life, as parts of one great system of Creation.*

* An account has recently been received from India of the discovery of an unknown and very curious fossil ruminating animal, nearly as large as an Elephant, which supplies a new and important link in the Order of Mammalia, between the Kuminantia and Pachydermata. A detailed description of this animal has been published by Dr. Falconer and Captain Cautley, who have given it the name of Savitherium, from the Sivalic or Sub-Himalayan range of hills in which it was found, between the Jumna and the Ganges. In size it exceeded the largest Rhinoceros. The head has been discovered nearly entire. The front of the skull is remarkably wide, and retains the bony cores of two short thick and straight horns, similar in position to those of the four-horned Antelope of Hindoostan. The nasal bones are salient in a degree without example among Ruminants, and exceeding in this respect those of the Rhinoceros, Tapir, and Paleotherium, the only herbivorous animals that have this sort of struc

As the bones of all these animals found in the earliest series of the tertiary deposites are accompanied by the remains of reptiles, such as now inhabit the fresh waters of warm countries, e. g. the Crocodile, Emys, and Trionyx (see PI. 1, Figs. 80, 81, 82,) and also by the leaves and prostrate trunks of palm trees (PI. 1', Figs. 66, 67, 68, and PI. 56,) we cannot but infer that the temperature of France was much higher than it is at present, at the time when it was occupied by these plants and reptiles, and by Mammalia allied to families which are natives of some of the warmest latitudes of the present earth, e. g. the Tapir, Rhinoceros, and Hippopotamus.

The frequent intrusion of volcanic rocks is a remarkable accompaniment of the tertiary strata of the Eocene period, in various parts of Europe; and changes of level, resulting from volcanic agency, may partially explain the fact, that portions of the same districts became alternately the receptacles of fresh and salt water.

The fresh-water calcareous deposites of this period are also highly important, in relation to the general history of the origin of limestone, from their affording strong evidence of the sources whence carbonate of lime has been derived.* Mammalia of the Miocene Period.

ture. Hence there is no doubt that the Sivatherium was invested with a trunk like the Tapir. Its jaw is twice as large as that of a Buffalo, and larger than that of a Rhinoceros. The remains of the Sivatherium were accompanied by those of the Elephant, Mastodon, Rhinoceros, Hippopotamus, several Ruminantia, &c.

It is stated that there is a wider distance between the living Genera of the Order Pachydermata than between those of any other Order of Mammalia, and that many intervals in the series of these animals have been filled up by extinct Genera and Species, discovered in strata of the Tertiary series. The Sivatherium forms an important addition to the extinct Genera of this intermediate and connecting character. The value of such links with reference to considerations in Natural Theology will be alluded to elsewhere.

* We see that thermal springs, in volcanic districts, issue from the earth, so highly charged with carbonate of lime, as to overspread large tracts of country with beds of calcareous tufa, or travertino. The waters

The second or Miocene System of Tertiary Deposites, contains an admixture of the extinct genera of lacustrine mammalia, of the first or Eocene series, with the earliest.

that flow from the Lago di Tartaro, near Rome, and the hot springs of San Filippo, on the borders of Tuscany, are well-known examples of this phenomenon. These existing operations afford a nearly certain explanation of the origin of extensive beds of limestone in fresh-water lakes of the tertiary period, where we know them to have been formed during seasons of intense volcanic activily. They seem also to indicate the probable agency of thermal waters in the formation of still larger calcareous deposites at the bottom of the sea, during preceding periods of the secondary and transition series.

It is a difficult problem to account for the source of the enormous masses of carbonate of lime that compose nearly one-eighth part of the superficial crust of the globe. Some have referred it entirely to the secretions of marine animals; an origin to which we must obviously assign those portions of calcareous strata which are composed of comminuted shells and corallines: but, until it can be shown that these animals have the power of forming lime from other elements, we must suppose that they derived it from the sea, either direcOy, or through the medium of its plants. In either case, it remains to find the source whence the sea obtained, not only these supplies of carbonate of lime for its animal inhabitants, but also the still larger quantities of the same substance, that have been precipitated in the form of calcareous strata.

We cannot suppose it to have resulted, like sands and clays, from the mechanical detritus of rocks of the granitic series, because the quantity of lime these rocks contain, bears no proportion to its large amount among the derivative rocks.. The only remaining hypothesis seems to be, that lime was continually introduced to lakes and seas, by water that had percolated rocks through which calcareous earth was disseminated.

Although carbonate of lime occurs not in distinct masses among rocks of igneous origin, it forms an ingredient of lava and basalt, and of various kinds of trap rocks. The calcareous matter thus dispersed through the substance of these volcanic rocks, seems to afford a magazine from which percolating water, charged with carbonic acid gas, may, in the lapse of ages, have derived sufficient carbonate of lime to form all the existing strata of limestone, by successive precipitates at the bottom of ancient lakes and seas. Mr. De la Beche states the quantity of lime in granite composed of two-fifths quartz, two-fifths felspar, and one-fifth mica, to be 0.37; and in greenstone, composed of equal parts of felspar and hornblende, to be 7.29. (Geol. Researches,

« AnteriorContinuar »