of mechanical contrivances, which are now distributed among three distinct classes of the animal kingdom. If for the purpose of producing vertical movements in the water, the sternum of the living Ornithorhynchus assumes forms and combinations that occur but in one other genus of Mammalia, they are the same that co-existed in the sternum of the Ichthyosaurus of the ancient world; and thus, at points of time, separated from each other by the intervention of incalculable ages, we find an identity of objects effected by instruments so similar, as to leave no doubt of the unity of the design in which they all originated.

It was a necessary and peculiar function in the economy of the fish-like Lizard of the ancient seas, to ascend continually to the surface of the water in order to breathe air, and to descend again in search of food; it is a no less peculiar function in the Duck-billed Ornithorhynchus of our own days, to perform a series of similar movements in the lakes and rivers of New Holland.

The introduction to these animals, of such aberrations from the type of their respective orders to accommodate deviations from the usual habits of these orders, exhibits a union of compensative contrivances, so similar in their relations, so identical in their objects, and so perfect in the adaptation of each subordinate part, to the harmony and perfection of the whole; that we cannot but recognise throughout them all, the workings of one and the same eternal principle of Wisdom and Intelligence, presiding from first to last over the total fabric of Creation.

SECTION V.

INTESTINAL STRUCTURE OF ICHTHYOSAURUS AND OF FOSSIL FISHES.

FROM the teeth and organs of locomotion, we come next to consider those of digestion in the Ichthyosaurus. If there be any point in the structure of extinct fossil animals, as to which it should have seemed hopeless to discover any kind of evidence, it is the form and arrangement of the intestinal organs; since these soft parts, though of prime importance in the animal economy, yet being suspended freely within the cavity of the body, and unconnected with the skeleton, would leave no traces whatever upon the fossil bones.

It is impossible to have seen the large apparatus of teeth, and strength of jaws, which we have been examining in the Ichthyosauri, without concluding that animals furnished with such powerful instruments of destruction, must have used them freely in restraining the excessive population of the ancient seas. This inference has been fully confirmed by the recent discovery within their skeletons, of the halfdigested remains of fishes and reptiles, which they had devoured, (see Pl. 13, 14,) and by the farther discovery of Coprolites, (see Pl. 15,) i. e. of fœcal remains in a state of petrifaction, dispersed through the same strata in which these skeletons are buried. The state of preservation of these very curious petrified bodies is often so perfect, as to indicate not only the food of the animals from which they were derived, but also the dimensions, form, and structure of their stomach, and intestinal canal.*

* The following description of these Coprolites, is given in my me. moir on this subject, published in the Transactions of the Geological

On the shore at Lyme Regis, these Coprolites are so abundant that they lie in some parts of the lias like potatoes scattered in the ground; still more common are they in the lias of the Estuary of the Severn, where they are

Society of London, 1829, (vol. iii. N. s. part i. p. 224, with three plates.)

"In variety of size and external form, the Coprolites resemble oblong pebbles or kidney-potatoes. They, for the most part, vary from two to four inches in length, and from one to two inches in diameter. Some few are much larger, and bear a due proportion to the gigantic calibre of the largest Ichthyosauri; others are small, and bear a similar ratio to the more infantine individuals of the same species, and to small fishes: some are flat and amorphous, as if the substance had been voided in a semifluid state; others are flattened by pressure of the shale. Their usual colour is ash-gray, sometimes interspersed with black, and sometimes wholly black. Their substance is of a compact earthy texture, resembling indurated clay, and having a conchoidal and glossy fracture. The structure of the Coprolites at Lyme Regis is in most cases tortuous, but the number of coils is very unequal; the most common number is three: the greatest I have seen is six these variations may depend on the various species of animals from which they are derived; I find analogous variations in the tortuous intestines of modern Skates, Sharks, and Dog-fish. Some Coprolites, especially the small ones, show no traces at all of contortion.

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The sections of these fœcal balls, (see Pl. 15, Figs. 4, and 6,) show their interior to be arranged in a folded plate, wrapped spirally round from the centre outwards, like the whorls of a turbinated shell; their exterior also retains the corrugations and minute impressions, which, in their plastic state, they may have received from the intestines of the living animals. (See Pl. 15, Figs. 3, and 10 to 14.) Dispersed irregularly and abundantly throughout these petrified fœces, are the scales, and occasionally the teeth and bones of fishes, that seem to have passed undigested through the bodies of the Saurians; just as the enamel of teeth and sometimes fragments of bone, are found undigested both in the recent and fossil album græcum of hyænas. These scales are the hard bright scales of the Dapedium politum, and other fishes which abound in the lias, and which thus appear to have formed no small portion of the food of the Saurians. The bones are chiefly vertebræ of fishes and of small Ichthyosauri; the latter are less frequent than the bones of fishes, but still are sufficiently numerous, to show that these monsters of the ancient deep, like many of their successors in our modern oceans, may have devoured the small and weaker individuals of their own species."

similarly disposed in strata of many miles in extent, and mixed so abundantly with teeth and rolled fragments of the bones of reptiles and fishes, as to show that this region, having been the bottom of an ancient sea, was for a long period the receptacle of the bones and fœcal remains of its inhabitants. The occurrence of Coprolites is not, however, peculiar to the places just mentioned; they are found in greater or less abundance throughout the lias of England; they occur also in strata, of all ages that contain the reinains of carnivorous reptiles, and have been recognised in many and distant regions both of Europe and America.*

The certainty of the origin of these Coprolites is established by their frequent presence in the abdominal region of fossil skeletons of Ichthyosauri found in the lias of Lyme Regis. One of the most remarkable of these is represented in Pl. 13; the coprolitic matter loaded with fish-scales, within the ribs of these and similar specimens, is identical in appearance and chemical composition with the insulated coprolites that occur in the same strata with the skeletons.†

* Professor Jæger has recently discovered many Coprolites in the alum slate of Gaildorf in Wirtemberg; a formation which he considers to be in the lower region of that part of the new red sandstone formation which in Germany is called Keuper; and which contains the remains of two species of Saurians.

In the United States Dr. Dekay has also discovered Coprolites in the Green-sand formation of Monmouth, in New Jersey, see Pl. 15, Fig. 13.

†This specimen has been presented by Viscount Cole to the Geological Collection of the University of Oxford. It affords decisive proof that the substances in question cannot be referred to adventitious matter, placed accidentally in contact with the fossil body, inasmuch as the large coprolitic mass is enclosed between the back bone and the right and left series of ribs, of which the greater number remain nearly in their natural position. The quantity of this coprolite is prodigious, when compared with the size of the animal in which it occurs; and if we were not acquainted with the powers of the digestive organs of reptiles and fishes, and their capacity of gorging the larger animals that form their prey; the great space within these fossil skeletons of Ichthyosauri, which is occasionally filled with coprolitic matter, would appear inexplicable.

The preservation of such focal matter, and its conversion to the state of stone, result from the imperishable nature of the phosphate of lime, of which both bones, and the products of digested bones are equally composed.

The skeleton of another Ichthyosaurus in the Oxford Museum, from the lias at Lyme Regis, (Pl. 14) shows a large mass of fish scales, chiefly referable to the Pholidophorus, limbatus,* intermixed with coprolite throughout the entire region of the ribs; this mass is overlaid by many ribs, and although, in some degree perhaps, extended by pressure, it shows that the length of the stomach was nearly co-extensive with the trunk.

* According to Professor Agassiz, the scales of Pholidophorus limbatus, a species very frequent among the fossils of the lias, are more abundant than those of any other fish in the Coprolites found in that formation at Lyme Regis; and show that this species was the principal food of these reptiles. In Coprolites from the coal formation, near Edinburgh, he has also recognised the scales of Palæoniscus, and of other fishes that are often found entire in strata that accompany the coal of that neighbourhood. Scales of the Beryx armatus, a fish discovered by Mr. Mantell, in the chalk, occur in Coprolites derived from voracious fishes during the deposition of this formation.

A Coprolite from the lias, (Pl. 15, Eig. 3,) remarkable for its spiral convolutions, and vascular impressions, affords a striking example of the minute accuracy with which investigations are now conducted by naturalists, and of the kind of evidence which comparative anatomy contributes in aid of geological inquiry. On one side of this Coprolite, there is a small scale, (Fig. 3, a,) which I could only refer to some unknown fish, of the numerous species that occur in the lias. The instant I showed it to M. Agassiz, he not only pronounced its species to be the Pholidophorus limbatus; but at once declared the precise place which this scale had occupied upon the body of the fish. A minute tube upon its inner surface, (Pl. 15, Fig. 3',) scarcely visible without a microscope, showed it to have been one of those which form the lateral line of perforated scales, that pass from the head towards the tail, one on each side of every fish: and convey a tube for the transmission of lubricating mucus from glands in the head, to the extremity of the body. The place of the scale in this line, had been on the left side, not far from the head. Fig. 3", is the upper surface of a similar scale, showing at e the termination of the mucous duct.