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neighboring fragments. These are held to be results of volcanic movements below, the operation of which is further seen in numerous upbursts and intrusions of fire-born rock (trap). That these disturbances took place about the close of the formation, and not later, is shown in the fact of the next higher group of strata being comparatively undisturbed. Other symptoms of this time of violence are seen in the beds of conglomerate which occur amongst the first strata above the coal. These, as usual, consist of fragments of the elder rocks, more or less worn from being tumbled about in agitated water, and laid down in a mud paste, afterwards hardened. Volcanic disturbances break up the rocks; the pieces are worn in seas: and a deposit of conglomerate is the consequence. Of porphyry, there are some such pieces in the conglomerate of Devonshire, three or four tons in weight. It is to be admitted for strict truth that, in some parts of Europe, the carboniferous formation is followed by superior deposits, without the appearance of such disturbances between their respective periods; but apparently this case belongs to the class of exceptions already noticed.* That disturbance was general, is supported by the further and important fact of the destruction of many forms of organic being previously flourishing, particularly of the vegetable kingdom.

"Some of the most considerable dislocations of the border of the coal fields of Coalbrookdale and Dudley, happened after the deposition of a part of the new red sandstone; but it is certain that those of Somersetshire and Gloucestershire were completed before the date of that rock."-Phillips.

69

ERA OF THE NEW RED SANDSTONE.

TERRESTRIAL ZOOLOGY COMMENCES

WITH REPTILES.

FIRST TRACES OF BIRDS.

THE next volume of the rock series refers to an era distinguished by an event of no less importance than the commencement of land animals. The New Red Sandstone System is subdivided into groups, some of which are wanting in some places: they are pretty fully developed in the north of England, in the following ascending order:-1, Lower red sandstone; 2, Magnesian limestone; 3, Red and white sandstones and conglomerate; 4, Variegated marls. Between the third and the fourth there is, in Germany, another group, called the Muschelkalk, a word expressing a limestone full of shells.

The first group, containing the conglomerates already adverted to, seems to have been produced during the time of disturbance which occurred so generally after the carbonigenous era. This new era is distinguished by a pau

city of organic remains, as might partly be expected from the appearance of disturbance, and the red tint of the rocks, the latter being communicated by a solution of oxide of iron, a substance unfavorable to animal life.

The second group is a limestone with an infusion of magnesia. It is developed less generally than some others, but occurs conspicuously in England and Germany. Its place, above the red sandstone, shows the recurrence of circumstances favorable to animal life, and we accordingly find in it not only zoophytes, conchifera, and a few tribes of fish, but some faint traces of land plants, and a new and startling appearance—a reptile of saurian (lizard) character, analogous to the now existing family called monitors. Remains of this creature are found in cupriferous (copper-bearing) slate connected with the mountain limestone, at Mansfield and Glucksbrunn, which may be taken as evidence that dry land existed in that age near those places. The magnesian limestone is also remarkable as the last rock in which appears the leptæna, or productus, a conchifer of numerous species which makes a conspicuous appearance in all previous seas. It is likewise to be observed, that the fishes of this age, to the genera of which the names palæoniscus, catopterus, platysomus, &c., have been applied, vanish, and henceforth appear no

more.

The third group, chiefly sandstones, variously colored according to the amount and nature of the metallic oxide infused into them, shows a recurrence of agitation, and a consequent diminution of the amount of animal life. In the upper part, however, of this group, there are abundant symptoms of a revival of proper conditions for such life. There are marl beds, the origin of which substance in de

composed shells is obvious; and in Germany, though not in England, here occurs the muschelkalk, containing numerous organic remains (generally different from those of the magnesian limestone), and noted for the specimens of land animals, which it is the first to present in any considerable abundance to our notice.

These animals are of the vertebrate sub-kingdom, but of its lowest class next after fishes,—namely, reptiles—a portion of the terrestrial tribes whose imperfect respiratory system perhaps fitted them for enduring an atmosphere not yet quite suitable for birds or mammifers.* The specimens found in the muschelkalk are allied to the crocodile and lizard tribes of the present day, but in the latter instance are upon a scale of magnitude as much superior to present forms as the lepidodendron of the coal era was superior to the dwarf club-mosses of our time. These saurians also combine some peculiarities of structure of a most extraordinary character.

The animal to which the name ichthyosaurus has been given, was as long as a young whale, and it was fitted for living in the water, though breathing the atmosphere. It had the vertebral column and general bodily form of a fish, but to that were added the head and breast-bone of a lizard, and the paddles of the whale tribes. The beak, moreover, was that of a porpoise, and the teeth were those of a crocodile. It must have been a most destructive creature to the fish of those early seas.

* The immediate effects of the slow respiration of the reptilia are, a low temperature in their bodies, and a slow consumption of food. Requiring little oxygen, they could have existed in an atmosphere containing a less proportion of that gas to carbonic acid than what now obtains.

The plesiosaurus was of similar bulk, with a turtle-like body and paddles, showing that the sea was its element, but with a long serpent-like neck, terminating in a saurian head, calculated to reach prey at a considerable distance. These two animals, of which many varieties have been discovered, constituting distinct species, are supposed to have lived in the shallow borders of the seas of this and subsequent formations, devouring immense quantities of the finny tribes. It was at first thought that no creatures approaching them in character now inhabit the earth; but latterly Mr. Darwin has discovered, in the reptile-peopled Galapagos Islands, in the South Sea, a marine saurian from three to four feet long.

The megalosaurus was an enormous lizard—a land creature, also carnivorous. The pterodactylus was another lizard, varying in size between a cormorant and a snipe, and furnished with unusually prolonged anterior extremities, supposed to have served, like those of the bat tribe, as wings, wherewith to pursue its prey in the air, though M. Agassiz, on the contrary, believes this animal to have been designed for an aquatic life. Crocodiles abounded, and some of these were herbivorous. Such was the iguanodon, a creature of the character of the iguana, but probably sixty feet in length, or twelve times that of its modern representative.

There were also numerous tortoises, some of them reaching a great size; and Professor Owen has found in Warwickshire some remains of an animal of the batrachian order,* to which, from the peculiar form of the teeth, he has given the name of labyrinthodon. Thus, three of

* The order to which frogs and toads belong.

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