creation; we have seen in proceeding through our examination of its details, that these apparent anomalies consist only in the diversified arrangement, and varied proportion, of parts fundamentally the same as those that occur in the most perfectly formed creatures of the present world.

Pursuing the analogies of construction, that connect the existing inhabitants of the earth with those extinct genera and species which preceded the creation of our race, we find an unbroken chain of affinities pervading the entire series of organized beings, and connecting all past and present forms of animal existence by close and harmonious ties. Even our own bodies, and some of their most important organs, are brought into close and direct comparison with those of reptiles, which, at first sight, appear the most monstrous productions of creation; and in the very hand and fingers with which we write their history, we recognise the type of the paddles of the Ichthyosaurus and Plesiosaurus.

Extending a similar comparison through the four great classes of vertebral animals, we find in each species a varied adaptation of analogous parts, to the different circumstances and conditions in which it was intended to be placed. Ascending from the lower orders, we trace a gradual advancement in structure and office, till we arrive at those whose functions

are the most exalted: thus, the fin of the fish becomes the paddle of the reptile Plesiosaurus and Ichthyosaurus; the same organ is converted into the wing of the Pterodactyle, the bird and bat; it becomes the fore-foot, or paw, in quadrupeds that move upon the land, and attains its highest consummation in the arm and hand of rational man.

I will conclude these observations in the words and with the feelings of Mr. Conybeare, which must be in unison with those of all who have had the pleasure to follow him through his masterly investigations of this curious subject, from which great part of our information respecting the genus Plesiosaurus has been derived:

"To the observer actually engaged in tracing the various links that bind together the chain of organized beings, and struck at every instant by the development of the most beautiful analogies, almost every detail of comparative anatomy, however minute, acquires an interest, and even a charm; since he is continually presented with fresh proof of the great general law, which Scarpa himself, one of its most able investigators, has so elegantly expressed: Usque adeo natura, una eadem semper atque multiplex, disparibus etiam formis effectus pares, admirabili quadam varietatum simplicitate conciliat.'"

SECTION VII.

MOSASAURUS, OR GREAT ANIMAL OF MAESTRICHT.

THE Mosasaurus has been long known by the name of the great animal of Maestricht, occurring near that city, in the calcareous freestone which forms the most recent deposit of the cretaceous formation, and contains Ammonites, Belemnites, Hamites, and many other shells belonging to the chalk, mixt with numerous remains of marine animals that are peculiar to itself. A nearly perfect head of this animal was discovered in 1780, and is now in the Museum at Paris. This celebrated head during many years baffled all the skill of Naturalists; some considered it to be that of a Whale, others of a Crocodile; but its true place in the animal kingdom was first suggested by Adrian Camper, and at length confirmed by Cuvier. By their investigations it is proved to have been a gigantic marine reptile, most nearly allied to the Monitor.* The geological epoch at which the Mosasaurus

* The Monitors form a genus of Lizards, frequenting marshes and the banks of rivers in hot climates; they have received this name from the prevailing, but absurd, notion that they give warning by a whistling noise, of the approach of Crocodiles and Caymans. One species, the Lacerta nilotica, which devours the eggs of Crocodiles, has been sculptured on the monuments of ancient Egypt.

first appeared, seems to have been the last of the long series, during which the oolitic and cretaceous groupes were in process of formation. In these periods the inhabitants of our planet seem to have been principally marine, and some of the largest creatures were Saurians of gigantic stature, many of them living in the sea, and controlling the excessive increase of the then existing tribes of fishes.

*

From the lias upwards, to the commencement of the chalk formation, the Ichthyosauri and Plesiosauri were the tyrants of the ocean; and just at the point of time when their existence terminated, during the deposition of the chalk, the new genus Mosasaurus appears to have been introduced, to supply for a while their place and office, being itself destined in its turn to give place to the Cetacea of the tertiary periods. As no Saurians of the present world are inhabitants of the sea, and the most powerful living representatives of this order, viz. the Crocodiles, though living chiefly in water, have recourse to stratagem rather than speed, for the capture of their prey, it may not be unprofitable to examine the mechanical contrivances, by which a reptile, most nearly allied to the Monitor, was so constructed, as to possess the power of moving in the sea, with sufficient velocity to

Remains of the Mosasaurus have been discovered by Mr. Mantell in the upper chalk near Lewes, and by Dr. Morton in the green sand of Virginia.

overtake and capture such large and powerful fishes, as from the enormous size of its teeth and jaws, we may conclude it was intended to devour.

The head and teeth, (Pl. 20.) point out the near relations of this animal to the Monitors; and the proportions maintained throughout all the other parts of the skeleton warrant the conclusion, that this monstrous Monitor of the ancient deep was five and twenty feet in length, although the longest of its modern congeners does not exceed five feet. The head here represented measures four feet in length, that of the largest Monitor does not exceed five inches. The most skilful Anatomist would be at a loss to devise a series of modifications, by which a Monitor could be enlarged to the length and bulk of a Grampus, and at the same time be fitted to move with strength and rapidity through the waters of the sea; yet in the fossil before us, we shall find the genuine characters of a Monitor maintained throughout the whole skeleton, with such deviations only as tended to fit the animal for its marine existence.

*

The Mosasaurus had scarcely any character in common with the Crocodile, but resembled the Iguanas, in having an apparatus of teeth fixed on the pterygoid bone, (Pl. 20, k.) and placed in the roof of its mouth, as in many

The Grampus is from 20 to 25 feet long, and very ferocious, feeding on seals and porpoises as well as on fishes.