FORM AND HABITS OF THE LIVING ANIMAL. 243

the form of its paddles; that its element was the sea, may be equally inferred from the remains with which it is universally associated; and that it may have occasionally visited the shore, the resemblance of its extremities to those of the turtle may lead us to conjecture. Its motion on land, however, must have been very awkward. Its long neck would impede its progress through water; presenting a striking contrast to the swimming organization, which fitted the ichthyosaurus to cleave the waves. May it not therefore be concluded, says the Rev. Mr. Conybeare, since its respiration required frequent access of air, that it swam upon or near the surface, arching back its long neck like the swan, and occasionally darting it down at the fish which happened to float within its reach? It may perhaps have lurked in shoal water along the coast, concealed among the sea-weed, and raising its nostrils, like the alligator, to a level with the surface, may have found a secure retreat from the assaults of powerful land enemies. By the suddenness and agility of its attack, it might easily make a prey of all the feebler animals which came within the sweep of its neck.

In the first part of the Philosophical Transactions for 1825, there is a most interesting communication by Gideon Mantell, Esq. on the teeth and bones of a fossil herbivorous reptile found in the sandstone of Tilgate forest, a part of the iron-sand formation, which forms in Sussex a chain of hills that stretches through the county in a W.N.W. direction, from Hastings to Horsham; whence it has been recently called the Hastings-sand formation. In various

parts of its course, but more particularly in the country around Tilgate and St. Leonard's forests, the sandstone contains the remains of saurian animals, turtles, birds, fishes, shells, and vegetables. Of the saurians, three if not four species belonging to as many genera are known to occur; viz. the crocodile, megalosaurus, plesiosaurus, and the iguanodon, the animal whose teeth form the subject of Mr. Mantell's paper.

The teeth of the crocodile, megalosaurus, and plesiosaurus, differ so materially from each other, and from those of the other lacertæ, as to be identified without difficulty; but in the summer of 1822, others were discovered in the same strata, which although evidently referable to some herbivorous reptile, possessed characters so remarkable, that the most superficial observer would have been struck with their appearance, as indicating something novel and interesting.

Mr. Mantell compared these singular teeth with those of the recent lacertæ in the Museum of the Royal College of Surgeons. The result of this examination proved highly satisfactory, for in an iguana, teeth were discovered possessing the form and structure of the fossil specimens. The tooth figured in the margin represents the outer surface of one of the largest and most perfect specimens of the teeth of the iguanodon. Here we see, the surface

of the tooth worn down obliquely by mastica

MARVELLOUS IGUANODON OF MANTELL. 245

tion; its serrated edges; the fang broken, and the hollow filled with sandstone; and the cavity or depression in the base of the fang, the effect of absorption caused by the pressure of a secondary tooth. The figure is of full size.

Like the teeth of the recent iguana, the crown of this tooth is acuminated; the edges are strongly serrated or dentated; the outer surface is ridged, and the inner smooth and convex. The teeth appear to have been hollow in the young animals, and to have become solid in the adult.

If any inference may be drawn from the nature of the fossils, with which the remains of the iguanodon are associated, we may conclude that if amphibious, it was not of marine origin, but inhabited rivers or fresh-water lakes. If the fossil and recent animal bore the same relative magnitudes, as their teeth, the one figured above must have belonged to an individual upwards of 60 feet long; a conclusion concerning the iguanodon in perfect accordance with that deduced by Professor Buckland from a femur (thigh bone) and other bones in Mr. Mantell's possession. Some further remarks on this great reptile will be found in Book III. Chap. iii. section 2.

From Mr. Mantell's researches there is every reason to believe that the iguanodon had a very remarkable appendage to its head, a horn, equal in size to the lesser horn of the rhinoceros, and not very different in form. The relic which he found of this appendage, is externally of a dark brown colour; some parts of the surface being smooth, while others are rough and furrowed, as if by the

passage of blood vessels. It possesses an osseous structure without internal cavity; but does not seem to have been united to the skull by a bony union, as the horns of the mammalia are. Among living iguanas, the horned species are most abundant. The iguana cornuta, a native of St. Domingo, resembles the common iguana in size, colour, and general proportions. On the front of the head, between the eyes and nostrils, are seated four rather large, scaly tubercles; behind which rises an osseous conical horn or process covered by a single scale. That the fossil horn of Mr. Mantell was such an appendage, there can be no doubt. Its surface bears marks of the impression of an integument by which it was covered, and probably attached to the skull.-See Mantell's Geology of Sussex.

We cannot help admitting for the future, among our best established truths, that vast multitudes of` reptiles of marvellous magnitude and variety inhabited the seas, or covered the surface of the globe at the ancient epoch, in which were deposited the strata commonly denoted in France by the too indefinite term of Jura formation; living in a wide waste of waters and marshes, where they died and were buried aloof from mammiferous animals. Time will possibly complete our knowledge of many beings, whose ancient existence is inferred from a few bony relics; and from the ardour with which these researches are now cultivated on every side, that time is probably not far distant. "I doubt not," says M. Cuvier, "that in proportion as the discoveries already made become more perfect, new discoveries will be multiplied, and in a few years

INFERIOR MEMBERS OF LOWER OOLITES. 247

perhaps, I may have to acknowledge that the work just now finished, to which I have devoted so much labour, may appear but a superficial sketch, an opening glimpse, of the immense creations of the primeval world."* This modest conclusion of the illustrious naturalist of France is almost the only one of his, from which the learned world will withhold their assent. In zoological and anatomical knowledge, in acuteness of discrimination, sagacity of comparison, soundness of inference, and above all, in general enlargement of thought, his talents and genius have secured to the Ossemens Fossiles, a noble and enduring station among the trophies of

science.

§ V. INFERIOR MEMBERS OF THE THIRD OR LOWER SYSTEM OF OOLITES.

The neighbourhood of Bath affords the best type of the arrangement of this part of the mineral series. In this district the separate beds appear most strongly characterised, and most distinctly divided. We shall study them, as usual, in their ascending order; beginning with the lowest.

The following section of Down Cliff between Seaton and Thorncombe two miles west of Bridport harbour, will give an idea of this bed, from above downwards.

1. Inferior oolite and sand alternating, the sand at the surface passing into marl, about

Feet.

80

2. Sandy marl,

50

3. Rusty sand with ferro-argillaceous concretions, whose cavities are filled with sand,

4. Greenish-blue micaceous sandy marl, containing indurated concretions of similar constitution,

• Cuvier-Ossemens Fossiles. Tome V. Partie II. p. 487.

80