it forms a communication with a permanent subterranean sheet of water, affording plentiful supplies to the inhabitants of upland districts, which are above the level of natural springs.

A farther benefit which man derives from the disposition of the mineral ingredients of the secondary strata, results from the extensive diffusion of muriate of soda, or common salt, throughout certain portions of these strata, especially those of the new red sandstone formation. Had not the beneficient providence of the Creator laid up these stores of salt within the bowels of the earth, the distance of inland countries from the sea would have rendered this article of prime and daily necessity, unattainable to a large proportion of mankind : but, under the existing dispensation, the presence of mineral salt, in strata which are dispersed generally over the interior of our continents and larger islands, is a source of health, and daily enjoyment, to the inhabitants of almost every region of the earth.* Muriate of soda is also among the most abundant of the saline compounds formed by sublimation in the craters of volcanos.

With respect to the state of animal life, during the deposition of the Secondary strata, although the petrified remains of Zoophytes, Crustacea, Testacea, and Fishes, show that the seas in which these strata were formed, like those which gave birth to the Transition series, abounded with creatures referable to the four existing divisions of the animal kingdom, still the condition of the globe seems not yet to have been sufficiently advanced in tranquillity, to admit

* Although the most frequent position of rock salt, and of salt springs, is in strata of the new red sandstone formation, which has consequently been designated by some geologists as the saliferous system, yet it is not exclusively confined to them. The salt mines of Wieliczka and Sicily are in tertiary formations; those of Cardona in cretaceous; some of those in the Tyrol in the oolites; and near Durham there are salt springs in the coal formation.

of general occupation by warm-blooded terrestrial Mammalia.

The only terrestrial Mammalia yet discovered in any secondary stratum, are the small marsupial quadrupeds allied to the Opossum, which occur in the oolite formation, at Stonesfield, near Oxford. The jaws of two species of this genus are represented in Plate 2. A. B; the double roots of the molar teeth at once refer these jaws to the class of Mammalia, and the form of their crowns places them in the order of Marsupial animals. Two other small species have been discovered by Cuvier, in the tertiary formations of the basin of Paris, in the gypsum of Mont Martre.

The Marsupial Order comprehends a large number of existing genera, both herbivorous and carnivorous, which are now peculiar to North and South America, and to New Holland, with the adjacent islands. The kangaroo and opossum are its most familiar examples. The name of Marsupialia is derived from the presence of a large external marsupium, or pouch, fixed on the abdomen, in which the fœtus is placed after a very short period of uterine gestation, and remains suspended to the nipple by its mouth, until sufficiently matured to come forth to the external air. The discovery of animals of this kind, both in the secondary and tertiary formations, shows that the Marsupial Order, so far from being of more recent introduction than other orders of mammalia, is in reality the first and most ancient condition under which animals of this class appeared upon our planet: as far as we know, it was their only form during the secondary period; it was co-existent with many other orders in the early parts of the tertiary period; and its geographical distribution in the present creation, is limited to the regions we have above enumerated.*

*In a highly important physiological paper, in the Phil. Trans. Lon don, 1834, part ii. p. 349, Mr. Owen has pointed out "the most irrefragible evidence of creative foresight, afforded by the existing Marsupialia, in the peculiar modifications both of the maternal and fœtal system, de

The peculiar feature in the population of the whole series of secondary strata, was the prevalence of numerous and gigantic forms of Saurian reptiles. Many of these were

signed with especial reference to each other's peculiar condition." With respect to the final cause of these peculiarities, he conjectures that they have relation to an inferior condition of the brain and nervous system in the Marsupialia; and considers the more protracted period of viviporous utero gestation in the higher orders of Mammalia to be connected with their fuller development of the parts subservient to the sensorial functions; the more simple form and inferior condition of the brain in Marsupialia, being attended with a lower degree of intelligence, and less perfect condition of the organs of voice.

As this inferior condition of living Marsupialia shows this order to hold an intermediate place between viviparous and oviparous animals, forming, as it were, a link between Mammalia and Reptiles; the analogies afforded by the the occurrence of the more simple forms of other classes of animals in the earlier geological deposites, would lead us to expect also that the first forms of Mammalia would have been Marsupial.

In a recent letter to myself, Mr. Owen adds the following interesting particulars respecting the physiology of this remarkable class of animals. "Of the generality of the law, as regards the simple unconvoluted form of the cerebrum in the Marsupials, I have had additional confirmation from recent dissections of a Dasyurus and Phalangista. With an organization defective in that part which I believe to be essential to the docility of the horse, and sagacity of the dog, it is natural to suppose that the Marsupial series of warm-blooded quadrupeds would be insufficient for the great purposes of the Creator, when the earth was rendered fit for the habitation of man. They do, indeed, afford the wandering savages of Australia a partial supply of food; but it is more than doubtful that any of the species will be preserved by civilized man on the score of utility. The more valuable and tractable ruminants are already fast encroaching on the plains where the kangaroo was once the sole representative of the gramnivorous Mammalia.

“It is interesting, however to observe, that the Marsupials, including the Monotremes, form a very complete series, adapted to the assimilation of every form of organic matter; and no doubt, with enough of instinctive precaution, to preserve themselves from extermination, when surrounded with enemies of no higher intellectual powers than the Reptilia. It would, indeed, be a strong support to the consideration of them as a distinct ovoviviparous sub-class of Mammals, if they should be found as hitherto, to be the sole representatives of the highest class of vertebrata, in the secondary strata."-R. OWEN..

Beginning with the animal kingdom, we find the four great existing divisions of Vertebrata, Mollusca, Articulata, and Radiata, to have been coeval with the commencement of organic life upon our globe.*

No higher condition of Vertebrata has been yet discovered in the transition formation than that of fishes, whose history will be reserved for a subsequent chapter.

The Mollusca,† in the transition series, afford examples of several families, and many genera which seem at that time to have been universally diffused over all parts of the world. Some of these, (e. g. the Orthoceratite, Spirifer, and Producta) became extinct at an early period in the history of stratification, whilst other genera (as the Nautilus and Terebratula) have continued through all formations unto the present hour.

The earliest examples of Articulated animals are those

mains preserved in the several series of formations, by introducing over each, restored figures of a few of the most characteristic animals and vegetables that occupied the lands and waters, at the periods in which they were deposited.

It has not been found necessary, in discussing the history of fossil plants and animals, to constitute a single new class; they all fall naturally into the same great sections as the existing forms.-We are warranted in concluding that the older organic creations were formed upon the same general plan as at present. They cannot, therefore, be correctly described as entirely different systems of nature, but should rather be viewed as corresponding systems, composed of different details. The difference of these details arises mostly from minute specific distinctions; but sometimes, especially among terrestrial plants, certain crustacea, and reptiles, the differences are of a more general nature, and it is not possible to refer the fossil tribes to any known recent genus, or even family. Thus we find the problem of the resemblance of recent and fossil organic beings to resolve itself into a general analogy of system, frequent agreement in important points, but almost universal distinction of minute organization."-Phillips's Guide to Geology, p. 61-63, 1834.

In this great division, Cuvier includes a vast number of animals having soft bodies, without any articulated skeleton or spinal marrow, such as the Cuttlc-fish, and the inhabitants of univalve and bivalve shells.

afforded by the extinct family of Trilobites, (see Plates 45 and 46) to the history of which we shall devote peculiar consideration under the head of Organic Remains. Although nearly fifty species of these Trilobites occur in strata of the transition period, they appear to have become extinct before the commencement of the secondary series.

The Radiated Animals are among the most frequent organic remains in the transition strata; they present numerous forms of great beauty, from which I shall select the family of Crinoidea, or lily-shaped animals allied to Star-fish, for peculiar consideration in a future chapter. (See Pl. 47, Figs. 5, 6, 7.) Fossil corallines also abound among the radiata of this period, and show that this family had entered thus early upon the important geological functions of adding their calcarious habitations to the solid materials of the strata of the globe. Their history will also be considered in another chapter.

Remains of Vegetables in the Transition Series.

Some idea may be formed of the vegetation which prevailed during the deposition of the upper strata of the transition series, from the figures represented in our first plate (Fig. 1 to 13.) In the interior regions of this series, plants are few in number, and principally marine;* but in its superior regions, the remains of land plants are accumu lated in prodigious quantities, and preserved in a state which gives them a high and two-fold importance; first, as illustrating the history of the earliest vegetation that appeared upon our planet, and the state of climate and geological changes which then prevailed:t secondly, as affecting, in no small degree, the actual condition of the human race.

* M. A. Brongniart mentions the occurrence of four species of fucoids in the transition strata of Sweden and Quchec; and Dr. Harlan has described another species found in the Alleghany Mountains.

The nature of these vegetables, and their relations to existing species, will be considered in a future chapter.