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but frequently changing both in depth and in the nature of its deposits; the islands being the habitation of land animals, while the surrounding coasts afforded food and shelter for vast multitudes of fishes and other marine groups. The marine deposit, however, seems to have been nearly limited towards the west by a recently formed lias coast, leading us to suspect the existence of land extending westwards and northwards from the line of that bed. Possibly this land may have formed a broken ring surrounding a Mediterranean Sea, just as the two portions of the great continent of America, connected partly by the Isthmus of Darien, and partly by the chain of the West India islands, now enclose a tract under nearly similar conditions.

However this may be, the great eastern oolitic archipelago seems to have been limited towards the west by England, and perhaps terminated towards the north with the land which now forms the range of the Hartz mountains, the mountains of Saxony, and those of Bohemia. Throughout the whole tract the general conditions of deposit must have been nearly analogous; but there were many important modifications in detail, especially in the western, southern, and south-eastern part, where the older beds are most developed; while in the north-eastern and central districts, the newer beds are apparently the most important. The newest of all the deposits was a great fresh-water formation known as the Wealden group, occupying a portion of the south-east of England, and met with again in Hanover.

By a gradual change in the nature of the deposits, the whole oolitic range seems to have served as the

habitation and burial-place of many successive races of beings; but there is nowhere evidence of such considerable or violent change as would justify us in separating the series into two or more parts. The whole was probably continuous; and, although affected by contemporaneous and successive disturbances frequently repeated, these hardly involved any changes of great moment modifying the general result.

The inhabitants of the sea during the oolitic period include, as might be expected, a vast multitude of species. Of these some were attached permanently to marine bodies, and so were partly or entirely dependant on a particular mechanical, chemical, or mineralogical condition of the sea bottom; others were attached less permanently, possessing only imperfect powers of locomotion, and limited as to the depth at which they conveniently live; while there were others, again, swimming freely in the ocean, and limited only in their range by the nature of the supply of food. The first-mentioned of these groups includes the coral animal and many others of low organization, the next comprehends the encrinites, star-fishes, sea-urchins, &c., as well as a number of crustaceans and insects, and a large proportion of the animals enclosed in shells; while the last, in some respects the most important and interesting group, includes the more highly organized mollusca, the fishes, and the marine reptiles. It will be convenient to describe, first, these different groups of the inhabitants of the ocean, and then proceed to the account of the land animals of the period.

The corals of the oolitic seas formed some considerable reefs and islands, especially during the mid

dle part of the period; but the species then common resemble so closely those of existing seas in all important points of structure (fig. 65), that it will not be

Fig. 65

OOLITIC CORAL. (Astræa.)

necessary to describe them in detail. They differ, indeed, in specific, and often in generic character; but, in spite of this, there can be no doubt of the general analogy, and we find exactly the same set of contrivances adopted to provide that varied and

[graphic]

effectual resistance to the waves which characterizes the labours of the coral animal, and which are especially seen in those gigantic monuments of its labours distributed over a vast expanse of sea in the Tropics and the southern hemisphere.

The oolitic encrinites are neither more numerous nor more remarkable than those of an earlier period; and it would appear, indeed, as if the original form of the development of this tribe had by this time given way to a more advanced type. There are, however, still some, and those very pretty and interesting groups of these animals, amongst which we may enumerate a fossil well known to collectors in the west of England as the "pear" or "Bradford" Encrinite. This species grew from a large and swelling base attached to a rock or some marine substance; it was provided with a stout stem of moderate length, and the plates of the upper part, or

body, are singularly thick and strong. The rock immediately below a particular bed of clay (called the Bradford clay) seems to have been a favourite locality, since the remains are there found in great beauty. The stem, or stony column, terminated with five pairs of short arms rising immediately from the upper plates; and these, when expanded, collected food and conveyed it to the mouth.

Fig. 66

Although the encrinites are not extremely abundant in the oolitic rocks, the tribe of radiated animals, to which they belong, was still amply represented. Star-fishes, sea-eggs, and sea-urchins of various kinds and size are universally distributed, and exceedingly beautiful species of an extinct genus (Cidaris), provided with stout.calcareous spines, are found singularly perfect (fig. 66). It would hardly be thought possible, that animals provided, as these are, with a vast multitude of thick, heavy, and perfectly solid stony clubs, attached only to the shell at one point, should, notwithstanding, OOLITIC SEA-EGG.* (Cidaris.) be perfectly free in all its movements, and, in fact, be greatly assisted in its locomotion by such appendages. The spines or clubs, to those accustomed only to watch the habits of animals inhabiting the land, and therefore surrounded with air and not water, appear so heavy as to be almost clumsy; but, in fact, they are so little heavier than

In the specimen figured, the stony club-shaped spines are absent, as is often the case in fossils; but the small mammillated projections to which they were attached by sockets are very beautifully shewn.

water, that they are perfectly manageable in that element, and when used as spades in the soft wet sand, the animal moves with great rapidity, and in any direction by their aid. Most of the animals of this group inhabit the shore, or moderate depths at no great distance from shore.

The oolitic crustacea include an extensive series not very different from the lobster, the prawns (see fig. 67), and the king-crabs of the existing seas. Most

Fig. 67

LONG-CLAWED OOLITIC SHRIMP.
(Megachirus.)

of these are found in one particular spot in the north of Bavaria, in a peculiar fine-grained absorbent stone, much used for lithographic purposes. This stone is calcareous; it has a peculiar aspect and a remarkably delicate texture, and has, doubtless, Fig. 68

I

Fig. 69

INSECTS OF THE SECONDARY EPOCH.

been deposited from an impalpable mud.

The numerous fossils it contains, and they are even more remarkable for their perfect condition than their num

ber, include but few remains of ordinary mollusca,

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