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twenty-five feet. The noble head in the Paris Museum, of which we have casts in this country, is four feet long; that of a large existing Monitor does not measure more than five inches in length.

The fossil was found in the calcareous freestone, near Maastricht, the most recent deposit of the cretaceous formation, in company with Ammonites, Belemnites, and other organic remains of the chalk formation in 1780, and for some time adorned that city. But it was a very sphinx's riddle to be learned. Some thought it was an enormous crocodile; others would have it to be very like a whale; but at last Camper suggested, and Cuvier afterwards confirmed its true zoological relations.

Fancy a marine Monitor of the length and bulk of a Grampus, with four paddles instead of legs, and a high and deep oar-like tail formed for propelling the animal through the wave, instead of the long and slender tail of the living species-and you have some notion of the Mosasaur.

Its jaws and teeth were tremendous. Nothing comparable to them can be imagined, excepting the ancient caricature, which may be known to some of our readers, representing a learned gentleman in his robes, not quite at his ease, between a pair of Saurian jaws, worthy of Munchausen's creation, and underwritten,

A LAWYER AND A SAWYER.

The rush of the Mosasaur through the water must have been most rapid; and its whole structure bespeaks an agent for keeping down the larger races of ancient fishes, more active and destructive than the great Ichthyosaur itself.

The Paris specimen belonged to the collection of Hoffman, from whom it was said to have been taken by the chapter of Maastricht, by virtue of some droits vested in them, and was given up by the Dean to the French army when it invested the city. Fortunate was the inhabitant whose dwelling lay near the place where the head of the Mosasaur was deposited: for the story goes, that to prevent the possibility of injury to a prize, which the besiegers were determined to possess, the French cannoniers were enjoined not to point their artillery towards that part of the city which held the remains of this grand SeaDragon.

ANCIENT AMPHIBIOUS AND TERRESTRIAL

DRAGONS.

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Through many a dark and dreary vale

They passed, and many a region dolorous,

Rocks, caves, lakes, fens, bogs, dens, and shades of death."

PARADISE LOST.

Ir, with the eyes of the imagination aided by the lights afforded by the strata and the ancient inhabitants buried therein, we look back upon our earth when the forms of crocodilian reptiles first came upon it, we may picture to ourselves an oozy, spongy, reeky land, watered with wild rivers, and largely overspread by a vast expanse of lakes, on whose dreary, slimy banks gigantic crocodiles reposed amid enormous extinct bog-plants, or floated log-like in the fenny sunshine on their waters, while the silence of the desolate scene was broken by the clank of their monstrous jaws, as they ever and anon closed upon the bygone generations of fishes, or by the growlings and explosions of the distant volcano.

With, perhaps, one exception-the crocodile of the Ganges namely-none of the ancient crocodilians exhibit specific identity with the alligators, crocodiles, and gavials now existing. And while they differ from the present races, the modifications of their osseous structure in which they so vary, as well as from each other, are much greater than any of those by which the skeletons of the existing species differ among themselves.

"Not only," says Professor Owen, "do the form and proportions of the peripheral parts, as of the jaws, the teeth, and the locomotive extremities vary, but the spine or central axis of the skeleton, offers modifications of the articular surfaces of the component vertebræ, which are quite unknown in the alligators, crocodiles, and gavials of the present epoch. In these existing species the anterior surface of the vertebral centrum is concave, the posterior convex, except in the atlas and sacrum. But besides this mode of junction, Cuvier has recognised in the crocodilians of the secondary formations two other types of vertebral structure: in one of these the positions of the ball and socket are

reversed; in the other, and more common modification, both the articular surfaces of the vertebra are flat or slightly concave. Remains of extinct crocodilians, exhibiting all the three systems of vertebral articulation, occur in English formations."

The professor then divides the extinct British species, which, generally, agree with the existing crocodilians, into two sections. First, those with concavo-convex vertebræ: secondly, those with biconcave vertebræ.

In the first of these divisions he notices and describes a single species-Crocodilus Spenceri.

In the second he arranges and gives a description of the following: Suchosaurus cultridens, Goniopholis crassidens, Teleosaurus Chapmanni, Teleosaurus cadomensis, Teleosaurus asthenodeirus, Steneosaurus rostro-minor, Poikilopleuron Bucklandi, Streptospondylus Cuvieri, Cetiosaurus brevis, Cetiosaurus brachyurus, Cetiosaurus medius, and Cetiosaurus longus.

The destructive nature of these ancient inhabitants of the swamps which once occupied the place of the fair fields and cities of these islands, may be imagined from the multitude of weapons that armed their jaws.

It has been calculated that Teleosaurus cadomensis had one hundred and eighty, and Teleosaurus Chapmanni at least one hundred and forty teeth. The gavial of these degenerate days cannot boast of more than one hundred and twelve.

But terribly voracious as these and other crocodilians (the enormous Sewalik crocodilian for example*) must have been, their efforts in keeping down the animals of the ancient Fauna of Britain could only have been feeble compared with those leviathans the Cetiosauri, some of which, according to Professor Owen's well-grounded statement, must have rivalled the modern great whales in bulk, and which he holds-with reason, we think-were strictly aquatic, and most probably marine in their habits. The larger alligator of the Ganges has been known in our own times to descend beyond the brackish water of the delta into the sea, though now frightened from its propriety by the steam-paddles that constantly vex that sacred river.

The evidence from which Professor Owen comes to this conclusion rests on the sub-biconcave structure of the vertebræ, and the coarse cancellous tissue of the long bones, which show no trace of a medullary cavity. In the great expanse of the coracoid and pubic bones, he tells us, as compared with the Teleosaurs and crocodiles, the gigantic saurians in question manifested their close

* See the work of Dr. Falconer and Major Cautley above noticed, p. 316, note.

affinity to the true Enaliosaurs which formed the principal subject of our last chapter; whilst their essential adherence to the crocodilian type is marked by the long bones of the extremities, especially the metatarsals, and above all, by the toes being terminated by strong claws.

The main organ of swimming is, the professor adds, shown, by the strength and texture and vertical compression of the posterior caudal vertebræ, to have been a broad vertical tail; and the webbed feet, probably, were used only partially, in regulating the course of the swimmer, as in the puny Amblyrhynchus of the Gallapagos Islands.

But what is an Amblyrhynchus ?

There are terrestrial and marine Amblyrhynchi; but it is the aquatic species Amblyrhynchus cristatus, to which the professor alludes. Here is its portrait drawn by the master hand of Darwin:

"It lives exclusively on the rocky sea-beaches, and is never found, at least I never saw one, even ten yards inshore. It is a hideous-looking creature, of a dirty black colour, stupid and sluggish in its movements. The usual length of a full-grown one is about a yard, but there are some even four feet long: I have seen a large one which weighed twenty pounds. On the island of Albemarle, they seem to grow to a greater size than on any other. These lizards were occasionally seen some hundred yards from the shore, swimming about; and Captain Colnett in his voyage says, 'they go out to sea in shoals to fish.' With respect to the object, I believe he is mistaken; but the fact stated on such good authority cannot be doubted. When in the water the animal swims with perfect ease and quickness, by a serpentine movement of its body and flattened tail, the legs, during this time, being motionless and closely collapsed on its sides. A seaman on board sank one with a heavy weight attached to it, thinking thus to kill it directly; but when, an hour afterwards, he drew up the line, the lizard was quite active. Their limbs and strong claws are admirably adapted for crawling over the rugged and fissured masses of lava which everywhere form the coast. In such situations, a group of six or seven of these hideous reptiles may oftentimes be seen on the black rocks, a few feet above the surf, basking in the sun with outstretched legs."

This extraordinary animal, notwithstanding its digusting appearance, seems to be very harmless. Mr. Darwin found the sto. machs of all which he opened distended with minced sea-weed, a food for the procuring and comminution of which its teeth, unlike those of the crocodilians, are well adapted; nor does he recollect having observed this sea-weed in any quantity on the tidal rocks. He states his belief to be that it grows at the bottom at some little

distance from the coast, and he observes that, if such be the case, the object of the animals in going out to sea is explained.

Another peculiarity in the habits of this creature is thus noticed by the same acute and accurate observer:

"The nature of this lizard's food, as well as the structure of its tail, and the certain fact of its having been seen voluntarily swimming out at sea, absolutely prove its aquatic habits; yet there is in this respect one strange anomaly; namely, that when frightened it will not enter the water. From this cause it is easy to drive the lizards down to any little point overhanging the sea, where they will sooner allow a person to catch hold of their tail than jump into the water. They do not seem to have any notion of biting; but when much frightened they squirt a drop of fluid from each nostril. One day I carried one to a deep pool left by the retiring tide, and threw it in several times as far as I was able. It invariably returned in a direct line to the spot where I stood. It swam near the bottom, with a very graceful and rapid movement, and occasionally aided itself over the uneven ground with its feet. As soon as it arrives near the margin, but still being under water, it either tried to conceal itself in the tufts of sea-weed, or it entered some crevice. As soon as it thought the danger was past, it crawled out on the dry rock, and shuffled away as quickly as it could."

Mr. Darwin goes on to state that he several times caught this same lizard, by driving it down to a point, and though possessed of such perfect powers of diving and swimming, nothing would induce it to enter the water: as often as he threw it in, it returned in the manner above described by him. He thinks that this singular piece of apparent stupidity may, perhaps, be accounted for, by the circumstance that this reptile has no enemy whatever on shore, whereas at sea it must often fall a prey to sharks.

"Hence," adds Mr. Darwin, "probably urged by a fixed and hereditary instinct that the shore is its place of safety, whatever the emergency may be, it there takes refuge."*

And this innocuous herbivorous lizard is the only known example of a saurian of decided marine habits at the present period. Strong is the contrast between the lacertian inhabitants of the world of to-day and those which peopled it in the age of reptiles to which we must now return, and inquire into the state of things when the crocodilian dynasty prevailed.

Remains of the extinct crocodilians may be traced from the

* Journal of Researches into the Geology and Natural History of the various countries visited by H.M.S. Beagle, under the command of Captain FitzRoy, R.N. from 1832 to 1836. By Charles Darwin, Esq., M.A. F.R.S., Secretary to the Geological Society, a work rich in vivid and accurate descriptions of nature.

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