The chalk formations or “cretaceous group of beds” include strata of various mineral substances; but the white chalk which forms the cliffs of Dover and the adjoining coasts, and the downs and chalk quarries of the South of England, is the chief and most characteristic formation. Chalk, immense as are the masses in which it has been deposited, owes its origin to living actions; every particle of it once circulated in the blood or vital juices of certain species of animals, or of a few plants, that lived in the seas of the secondary period of geological time. White chalk consists of carbonate of lime, and is the result of the decomposition chiefly of coral-animals (Madrepores, Millepores, Flustra, Cellepora, &c.), of sea-urchins (Echini), and of shell-fishes (Testacea), and of the mechanical reduction, pounding, and grinding of their shells. Such chalk-forming beings still exist, and continue their operations in various parts of the ocean, especially in the construction of coral reefs and islands.
Every river that traverses a limestone district carries into the sea a certain proportion of caustic lime in solution: the ill effects of the accumulation of this mineral are neutralised by the power allotted to the above-cited sea-animals to absorb the lime, combine it with carbonic-acid, and precipitate or deposit it in the condition of insoluble chalk, or carbonate of lime.
The best known and most characteristic large extinct animal of the chalk formations is chiefly found in the uppermost and most recent division, and is called
No. 1.—The Mosasaurus.
(Mosasaurus Hoffmanni, Hoffmann’s Mosasaur.)
Of this animal almost the entire skull has been discovered, but not sufficient of the rest of the skeleton to guide to a complete restoration of the animal. The head only, therefore, is shown, of the natural size, at the left extremity of the Secondary Island.
The first or generic name of this animal is derived from the locality, Maestricht, on the river Meuse (Lat. Mosa), in Germany, where its remains have been chiefly discovered, and from the Greek word sauros, a lizard, to which tribe of animals it belongs. Its second name refers to its discoverer, Dr. Hoffmann, of Maestricht, surgeon to the forces quartered in that town in 1780. This gentleman had occupied his leisure by the collection of the fossils from the quarries which were then worked to a great extent at Maestricht for a kind of yellowish stone of a chalky nature, and belonging to the most recent of the secondary class of formations in geology. In one of the great subterraneous quarries or galleries, about five hundred paces from the entrance, and ninety feet below the surface, the quarrymen exposed part of the skull of the Mosasaurus, in a block of stone which they were engaged in detaching. On this discovery they suspended their work, and went to inform Dr. Hoffmann, who, on arriving at the spot, directed the operations of the men, so that they worked out the block without injury to the fossil; and the doctor then, with his own hands, cleared away the matrix and exposed the jaws and teeth, casts of which are shown in the cretaceous rock of the Island.
This fine specimen, which Hoffmann had added with so much pains and care to his collection, soon, however, became a source of chagrin to him. One of the canons of the cathedral at Maestricht, who owned the surface of the soil beneath which was the quarry whence the fossil had been obtained, when the fame of the specimen reached him, pleaded certain feudal rights to it. Hoffmann resisted, and the canon went to law. The Chapter supported the canon, and the decree ultimately went against the poor surgeon, who lost both his specimen and his money—being made to pay the costs of the action. The canon did not, however, long enjoy possession of the unique specimen. When the French army bombarded Maestricht in 1795, directions were given to spare the suburb in which the famous fossil was known to be preserved; and after the capitulation of the town it was seized and borne off in triumph. The specimen has since remained in the museum of the Garden of Plants at Paris.
This skull of the Mosasaurus measures four and a half feet long and two and a half feet wide. The large pointed teeth on the jaws are very conspicuous; but, in addition to these, the gigantic reptile had teeth on a bone of the roof of the mouth (the pterygoid), like some of the modern lizards. The entire length of the animal has been estimated at about thirty feet. It is conjectured to have been able to swim well, and to have frequented the sea in quest of prey: its dentition shows its predatory and carnivorous character, and its remains have hitherto been met with exclusively in the chalk formations. Besides the specimens from St. Peter’s Mount, Maestricht, of which the above-described skull is the most remarkable, fossil bones and teeth of the Mosasaurus have been found in the chalk of Kent, and in the green-sand—a member of the cretaceous series—in New Jersey, United States of America. No animal like the Mosasaurus is now known to exist.
Nos. 2 & 3.—The Pterodactyle.
Nos. 2 and 3 are restorations of a flying reptile or dragon, called Pterodactyle, from the Greek words pteron, a wing, and dactylos, a finger; because the wings are mainly supported by the outer finger, enormously lengthened and of proportionate strength, which, nevertheless, answers to the little finger of the human hand. The wings consisted of folds of skin, like the leather wings of the bat; and the Pterodactyles were covered with scales, not with feathers: the head, though somewhat resembling in shape that of a bird, and supported on a long and slender neck, was provided with long jaws, armed with teeth; and altogether the structure of these extinct members of the reptilian class is such as to rank them amongst the most extraordinary of all the creatures yet discovered in the ruins of the ancient earth.
Remains of the Pterodactyle were first discovered, in 1784, by Prof. Collini, in the lithographic slate of Aichstadt, in Germany, which slate is a member of the oolitic formations: the species so discovered was at first mistaken for a bird, and afterwards supposed to be a large kind of bat, but had its true reptilian nature demonstrated by Baron Cuvier, by whom it was called the Pterodactylus longirostris, or Long-beaked Pterodactyle: it was about the size of a curlew.
A somewhat larger species—the Pterodactylus macronyx, or Long-clawed Pterodactyle—was subsequently discovered by the Rev. Dr. Buckland, in the lias formation of Lyme Regis: its wings, when expanded, must have been about four feet from tip to tip. The smallest known species—the Pterodactylus brevirostris, or Short-beaked Pterodactyle—was discovered in the lithographic slate at Solenhofen, Germany, and has been described by Professor Soemmering.
Remains of the largest known kinds of Pterodactyle have been discovered more recently in chalk-pits, at Burham, in Kent. The skull of one of these species—the Pterodactylus Cuvieri—was about twenty inches in length, and the animal was upborne on an expanse of wing of probably not less than eighteen feet from tip to tip. The restored specimen of this species is numbered 3.
A second very large kind of Pterodactyle—the Pterodactylus compressirostris, or Thin-beaked Pterodactyle—had a head from fourteen to sixteen inches in length, and an expanse of wing, from tip to tip, of fifteen feet. The remains of this species have also been found in the chalk of Kent. From the same formation and locality a third large kind of Pterodactyle, although inferior in size to the two foregoing, has been discovered, called the Pterodactylus conirostris, and also—until the foregoing larger kinds were discovered—Pterodactylus giganteus. The long, sharp, conical teeth in the jaws of the Pterodactyles indicate them to have preyed upon other living animals; their eyes were large, as if to enable them to fly by night. From their wings projected fingers, terminated by long curved claws, and forming a powerful paw, wherewith the animal was enabled to creep and climb, or suspend itself from trees. It is probable, also, that the Pterodactyles had the power of swimming; some kinds, e.g., the Pterodactylus Gemmingi, had a long and stiff tail. “Thus,” writes Dr. Buckland, “like Milton’s Fiend, all qualified for all services and all elements, the creature was a fit companion for the kindred reptiles that swarmed in the seas, or crawled on the shores of a turbulent planet.
‘The Fiend,
O’er bog, or steep, through strait, rough, dense, or rare,
With head, hands, wings, or feet, pursues his way,
And swims, or sinks, or wades, or creeps, or flies.’
Paradise Lost, Book II.”
