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ture and functions of these extinct families of reptiles; and not only enables us to infer from the restoration of their skeletons, what may have been the external form of their bodies; but instructs us also as to their economy and habits, the nature of their food, and even of their organs of digestion. It farther shows their relation to the then existing condition of the world, and to the other forms of organic life with which they were associated.

The remains of these reptiles bear a much greater resemblance to one another, than to those of any animals we discover in deposites preceding or succeeding the secondary series.*

The species of fossil Saurians are so numerous, that we can only select a few of the most remarkable among them, for the purpose of exemplifying the prevailing conditions of animal life, at the periods when the dominant class of animated beings were reptiles; attaining, in many cases, a magnitude unknown among the living orders of that class, and which seems to have been peculiar to those middle ages of geological chronology, that were intermediate between the transition and tertiary formations.

During these ages of reptiles, neither the carnivorous nor lacustrine Mammalia of the tertiary periods had begun to appear; but the most formidable occupants, both of land and water, were Crocodiles, and Lizards; of various forms, and often of gigantic stature, fitted to endure the turbulence, and continual convulsions of the unquiet surface of our infant world.

When we see that so large and important a range has been assigned to reptiles among the former population of

* The oldest strata in which any reptiles have yet been found are those connected with the magnesian-limestone formation. (Pl. 1, Sec. 16.) The existence of reptiles allied to the Monitor in the cupriferous slate and zechstein of Germany, has long been known. In 1834, two species of reptiles, allied to the Iguana and Monitor, were discovered in the dolomitic conglomerate, on Durdham Down, near Bristol.

our planet, we cannot but regard with feelings of new and unusual interest, the comparatively diminutive existing orders of that most ancient family of quadrupeds, with the very name of which we usually associate a sentiment of disgust. We shall view them with less contempt, when we learn from the records of geological history, that there was a time when reptiles not only constituted the chief tenants and most powerful possessors of the earth, but extended their dominion also over the waters of the seas; and that the annals of their history may be traced back through thousands of years, antecedent to that latest point in the progressive stages of animal creation, when the first parents of the human race were called into existence.

Persons to whom this subject may now be presented for the first time, will receive, with much surprise, perhaps, almost with incredulity, such statements as are here advanced. It must be admitted, that they at first seem much more like the dreams of fiction and romance, than the sober results of calm and deliberate investigation; but to those who will examine the evidence of facts upon which our conclusions rest, there can remain no more reasonable doubt of the former existence of these strange and curious creatures, in the times and places we assign to them; than is felt by the antiquary, who, finding the catacombs of Egypt stored with the mummies of Men, and Apes, and Crocodiles, concludes them to be the remains of mammalia and reptiles, that have formed part of an ancient population on the banks of the Nile.

SECTION IV.

ICHTHYOSAURUS.

NEARLY at the head of the surprising discoveries, which have been made relating to the family of Saurians, we may rank the remains of many extraordinary species, which inhabited the sea; and which present almost incredible combinations of form, and structure; adapting them for modes of life that do not occur among living reptiles. These remains are most abundant throughout the lias and oolite formations of the secondary series. In these deposites we find not only animals allied to Crocodiles, and nearly approaching to the Gavial of the Ganges; but also still more numerous gigantic Lizards, that inhabited the then existing seas and estuaries.

Some of the most remarkable of these reptiles have been arranged under the genus Ichthyosaurus, (or Fish Lizard,) in consequence of the partial resemblance of their vertebræ to those of fishes. (See Plate 1, Fig. 51, and Plates 7, 8, 9.) If we examine these creatures with a view to their сараbilities of locomotion, and the means of offence and defence which their extraordinary structure afforded to them; we shall find combinations of form and mechanical contrivances

* The chief repository in which these animals have been found is the lias, at Lyme Regis; but they abound also along the whole extent of this formation throughout England, e. g. from the coast of Dorset, through Somerset and Leicestershire, to the coast of Yorkshire: they are found also in the lias of Germany and France. The range of the genus Ichthyosaurus seems to have begun with the Muschelkalk, and to have extended through the whole of the oolitic period into the cretaceous formation. The most recent stratum in which any remains of this genus have yet been found is the chalk marl at Dover, where they have been discovered by Mr. Mantell: I have found them in the gault, near Benson, Oxon.

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which are now dispersed through various classes and orders of existing animals, but are no longer united in the same genus. Thus, in the same individual, the snout of a Porpoise is combined with the teeth of a crocodile, the head of a Lizard with the Vertebræ of a fish, and the sternum of an Ornithorhynchus with the paddles of a whale. The general outline of an Ichthyosaurus must have most nearly resembled the modern Porpoise, and Grampus. It had four broad feet, or paddles, (Pl. 7,) and terminated behind in a long and powerful tail. Some of the largest of these reptiles must have exceeded thirty feet in length.

There are seven or eight known species of the genus Ichthyosaurus, all agreeing with one another in the general principles of their construction, and the possession of those peculiar organs, in which I shall endeavour to point out the presence of mechanism and contrivance, adapted to their habits and state of life. As it will be foreign to our purpose to enter on details respecting species, I shall content myself with referring to the figures of the four most common forms (Plates 7, 8, 9.)

* Pl. 7, is a large and nearly perfect specimen of the Ichthyosaurus Platyodon, from the lias at Lyme Regis, being one of the splendid series of Saurians, purchased in 1834 of Mr. Hawkins by the British Museum. Portions of the paddles, and many lost fragments, are restored from the corresponding parts which are preserved; a few vertebræ, and the extremity of the tail are also restored conjecturally. Beautiful and accurate lithographed figures of this specimen, and of the greater part of this collection, are published in Mr. Hawkins's Memoirs of Ichthyosauri and Plesiosauri, London, 1834. Pl. 8. Fig. 1, is a small specimen of the Ichthyosaurus Communis, from the lias at Lyme Regis, belonging to the Geol. Soc. of London. Pl. 8, Fig. 2, a small Ichthyosaurus Intermedius, from the lias at Lyme Regis belonging to Sir Astley Cooper. Pl. 9, Fig. 1, an Ichchyosaurus Tenuirostris, from the lias of Street, near Glastonbury, in the collection of Rev. D. Williams. Fig. 2 is the continuation of the tail, and Fig. 3, the The teeth in this species are small, and in due propor

reverse of the head.
tion to the slender character of the snout.

Head.

The head, which in all animals forms the most important and characteristic part, (see Pl. 10, Figs. 1, 2,) at once shows that the Ichthyosauri were Reptiles, partaking partly of the characters of the modern Crocodiles, but more allied to Lizards. They approach nearest to Crocodiles in the form and arrangement of their teeth. The position of the nostril is not, as in Crocodiles, near the point of the snout; it is set, as in Lizards, near the anterior angle of the orbit of the eye. The most extraordinary feature of the head, is the enormous magnitude of the eye, very much exceeding that of any living animal.* The expansion of the jaws must have been prodigious; their length in the larger species, (Ichthyosaurus Platyodon,) sometimes exceeding six feet; the voracity of the animal was doubtless in proportion to its powers of destruction. The neck was short, as in fishes.

Teeth.

The teeth of the Ichthyosaurus (Pl. 11, в, c,) are conical, and much like those of the Crocodiles, but considerably more numerous, amounting in some cases to a hundred and eighty; they vary in each species; they are not enclosed in deep and separate sockets, as the teeth of Crocodiles, but are ranged in one long continuous furrow, (Pl. 11, в, c,) of the maxillary bone, in which the rudiments of a separation into distinct alveoli may be traced in slight ridges extending between the teeth, along the sides and bottom of the furrow. The contrivance by which the new tooth replaces the old one, is very nearly the same in the Ichthyosauri as in the Crocodiles (Pl. 11, A, B, C ;) in both, the young tooth begins its growth at the base of the old tooth, where, by pressure

* In the collection of Mr. Johnson, at Bristol, is a skull of Ichthyosaurus Platyodon, in which the longer diameter of the orbital cavity measures fourteen inches.

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