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 Marsupialia is derived from the presence of a large external marsupium, or pouch, fixed on the abdomen, in which the foetus 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. London, 1834, part ii. p. 349, Mr. Owen has pointed out "the most irrefragable evidence of creative foresight, afforded by the existing Marsupialia, in the peculiar modifications both of the maternal and foetal system, designed with especial reference to

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 exclusively marine; others amphibious; others were terrestrial, ranging in savannahs and jungles, clothed with a tropical vegetation, or basking on the margins of estuaries, lakes, and rivers. Even the air was tenanted by flying lizards, under the dragon

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 viviparous utero-gestation in the higher orders of Mammalia to be connected with their fuller developement 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 occurrence of the more simple forms of other classes of animals in the earlier geological deposits, 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 insuf

form of Pterodactyles. The earth was probably at that time too much covered with water, and those portions of land which had emerged above the surface, were too frequently agitated by earthquakes, inundations, and atmospheric irregularities, to be extensively occupied by any higher order of quadrupeds than reptiles.

As the history of these reptiles, and also that of the vegetable remains,* of the secondary for

ficient 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 graminivorous 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.

*The vegetable remains of the secondary strata differ from those of the transition period, and are very rarely accumulated into beds of valuable coal. The imperfect coal of the Cleveland Moorlands near Whitby, on the coast of Yorkshire, and that of Brora in the county of Sutherland, occurs in the lower region of the oolite formation; that of Bückeberg in Nassau, is in the lower region of the same formation, and is of superior quality.

mations, will be made a subject of distinct inquiry, it will here suffice to state, that the proofs of method and design in the adaptation of these extinct forms of organization to the varied circumstances and conditions of the earth's progressive stages of advancement, are similar to those we trace in the structure of living animal and vegetable bodies; in each case, we argue that the existence of contrivances, adapted to produce definite and useful ends, implies the anterior existence and agency of creative intelligence.

CHAPTER IX.

Strata of the Tertiary Series.

THE Tertiary Series introduces a system of new phenomena, presenting formations in which the remains of animal and vegetable life approach gradually nearer to species of our own epoch. The most striking feature of these formations consists in the repeated alternations of marine deposits, with those of fresh water (see Pl. 1, sect. 25, 26, 27, 28).

We are indebted to Cuvier and Brongniart, for the first detailed account of the nature and relations of a very important portion of the

tertiary strata, in their inestimable history of the deposits above the chalk near Paris. For a short time, these were supposed to be peculiar to that neighbourhood; further observation has discovered them to be parts of a great series of general formations, extending largely over the whole world, and affording evidences of, at least, four distinct periods, in their order of succession, indicated by changes in the nature of the organic remains that are imbedded in them.*

Throughout all these periods, there seems to have been a continually increasing provision for the diffusion of animal life, and we have certain evidence of the character and numbers of the

*We owe to Mr. Webster, the first discovery of the Tertiary strata in the I. of Wight, and S. E. Part of England. (See Geol. Trans. Lond. O. S. Vol. 2. p. 161.)

Mr. Lyell, in Vol. II. of his Principles of Geology, has given an interesting map, showing the extent of Europe, which has been covered by water since the commencement of the Tertiary strata.

M. Boué, also, has published an instructive map, representing the manner in which central Europe was once divided into a series of separate basins, each maintaining, for a long time, the condition of a fresh-water lake; those which were subject to occasional irruptions of the sea, would, for a while, admit of the deposition of marine remains; the subsequent exclusion of the sea, and return to the condition of a fresh-water lake, would allow the same region to become the receptacle of the exuviæ of animals inhabiting fresh water.-Synoptische Darstellung der Erdrinde. Hanau, 1827. The same map, on a larger scale, appears in the 2nd series of the Trans. of the Linn. Soc. of Normandy.

In the Annals of Philosophy, 1823, the Rev. W. D. Conybeare published an admirable memoir, illustrative of a similar geological map of Europe.