state of progression, from the earliest periods of the earth's history. In the case of fossil shells, as well as other organic remains, a great proportion bear a strong analogy to such as are now only known to inhabit tropical seas.

Figures C and D are specimens of two species of a crustaceous marine animal which has been wholly extinct from an early period in the formation of the crust of the globe; myriads of ages may have elapsed since it ceased to exist. It has not been found in any rock lying above the mountain limestone, and that rock is so low in the series of the strata, that the earth must have undergone many successive revolutions, each separated by an interval of vast duration, since the time when these animals were inhabitants of the sea. There are several species of the animal, which has been called Trilobite, from the body being composed of three longitudinal divisions or lobes. It was first brought under the notice of naturalists by the name of the Dudley fossil, being found very frequently in the limestone near the town of that name in Worcestershire, not far from Birmingham. It is met with in some spots in such immense quantities that it must have had prodigious powers of multiplication. In some parts of Wales the slate is so full of fragments of the animal that millions must have swarmed on the spot.

Another fossil animal which is very peculiar in its form, is that represented in fig. E, called the lily encrinite. It resembles that flower upon its stalk, and still more so when the several parts of which the flower-like extremity is composed, are separated and spread out; specimens of it in this state are not unfrequently met with. The animal lived in the base of the flower, and the separable parts stretched out like arms to seize its prey. It was fixed to the ground by the other extremity of the stalk. That stalk is not a single piece, but consists of a number of distinct joints like those of the back-bone, or like a necklace of beads, on which account the fossil has been sometimes called Encrinites Moniliformis, or necklace-form encrinite. The stalk is perforated through its whole length, and the joints when separated have figured surfaces, such as are represented in the engraving in the circular bodies, a, b, c, d, e, the figure being different at different parts of the stalk. This family of radiated animals, which consists of many extinct genera and species, has not wholly disappeared like the trilobite and ammonite; living representatives of it are still found in the seas of the West Indies; but the lily encrinite, that branch of the family, is not only wholly extinct, but has been so ever since the period when the (Fig. E.) new red sandstone was deposited. It appears to have had comparatively a short existence, for it has only been found in a limestone which occurs associated with the new red sandstone.

By far the most remarkable fossil remains of extinct marine animals, are certain species which resemble the crocodile and alligator, and often of a magnitude which these never reach; these extraordinary creatures were inhabitants of our planet at a period of its history, when the climate of the sea that covered the deposites now forming the cliffs of Lyme Regis, in Dorsetshire, was as hot as the West Indies.

Skeleton of the Plesiosaurus Dolichodeirus, in the position in which it was found at Lyme Regis.

The most remarkable of the fossil saurians which are found in the secondary strata are those which have been called ichthyosaurus, plesiosaurus, megalosaurus, and iguanodon. The first of these is so called from the characters of the animal partaking at the same time of the nature of a fish and of the lizard tribe; ichthys and saurus being two Greek words signifying fish and lizard. Its head resembles that of a crocodile, only it is much larger and sharper, its snout ending in a point, almost as acute as the beak of a bird: it has a most formidable supply of sharp conical teeth, no less than sixty in each jaw. Its head was of an enormous size, for jaws measuring eight feet in length have been found; and it was furnished with a pair of eyes of still more extraordinary proportion, for the oval hollows for that organ in a skull belonging to a gentleman at Bristol, measure fourteen and a half inches in their largest diameter, the size of a dish on which a tolerably good-sized turkey could be served up. The head was about a fourth of the whole length of the animal, and was joined to the body by a very short neck: the back-bone was composed of joints or vertebræ different from those of land animals, and similar to those of fishes; it was supplied with four paddles like those of a turtle, in the lower part of its body, and by means of these and its very powerful tail, it must have darted very swiftly through the water. It was a most singular combination of forms, for it had the snout of a dolphin, the teeth of a crocodile, the head and breast-bone of a lizard, extremities like the marine mammalia, and vertebræ like a fish. We can, however. form no idea of the appearance of the animal when alive, except such as is conveyed to us by the sight of the skeleton; a very imperfect one, no doubt, as we know by the difference between any animal and its skeleton placed beside it. The preceding representation of the complete skeleton of the ichthyosaurus, as restored in the way we have alluded to, is given by the Rev. W. Conybeare, the eminent geologist to whom we are indebted for the most complete account of these fossil saurians.

Remains of the ichthyosaurus have been found in all the secondary strata, between the red sandstone and the chalk in many parts of England; but they are most frequently met with in the lias limestone, and in greatest abundance at Lyme Regis in Dorsetshire. They have also been found in several places on the continent, especially in Wurtemburgh.

The plesiosaurus is so called from its near approach to the lizard tribe, plesion being the Greek for near. It has a considerable resemblance in the body to the ichthyosaurus, but the head is much smaller, and is altogether of a different structure; but its most remarkable character is the great length of its neck. In man, all quadrupeds and other mammalia, there are exactly seven joints or vertebræ in the neck; and so strict is the adherence to this rule, that there is precisely the same number in the short, stiff neck of the whale, and the long flexible neck of the giraffe. Reptiles have from three to eight joints-birds many more; the swan, which has the most, is enabled to make the graceful curves of its neck by being provided with twentythree of those separate vertebræ ; but the plesiosaurus had no less than forty-one. In order to convey to our readers an idea of the state in which fossil-bones are found, we have given a representation of a plesiosaurus, found in 1823 at Lyme Regis; but we must remark that, mutilated as it seems, it is rare to find bones lying so nearly in the form of the skeleton as those are. The specimen occurred imbedded in the shale or slaty clay, which lies between the beds of lias limestone, and the skeleton has been crushed almost flat by the vast weight of stone lying above it.

Mr. Conybeare, to whom we are indebted for the first description and name of the plesiosaurus, has given us the representation on page 19, of this extraordinary longnecked reptile, in a restored state, in the same way as he has given us a figure of the ichthyosaurus.

Some fragments of the bones of a saurian of gigantic size were discovered by Dr. Buckland a few years ago in the quarry of Stonesfield, near Woodstock, in Oxfordshire. According to the opinion of Cuvier, who examined them, they must have belonged to an individual of the lizard tribe, measuring forty feet in length, and having a bulk equal to that of an elephant seven feet high. This fossil animal was distinguished by Dr. Buckland with the name of megalosaurus, on account of its great size, megale being Greek for great.

In Cornwall and Devonshire, eminences of granite, serpentine, and felspar porphyry, occur, while the slopes resting on them are composed of different kinds of slate. The granite of this district is extensively used for paving in London, though considered less hard and durable than that brought from Scotland. In other places

the granite often assumes remarkable shapes. The Cheesewring is a natural pile or combination of rude granite rocks, in the parish of St. Cleer, Cornwall, between Liskeard and Launceston. It rises to the height of thirty-two feet, and stands near the top of a high hill. The stones are placed one upon another, and from the shape of the pile (probably resembling an ancient cheesepress) the name appears to have been derived. It consists of eight stones, of which the upper ones are so much larger than those below, and project so far over the middle and base, that it has for many generations excited astonishment how so ill-constructed a pile could have resisted the storms of such an exposed situation. Some art may possibly have been used in reducing the size of one of the central stones, and in clearing the base from circumjacent rocks, but otherwise this curiosity is entirely a work of nature.

On the same hill are several other similar piles of granite rocks, but not one of them is so singular in its relative proportions. One stone is of the enormous measurement of eleven yards in length, nine yards in breath, with an average thickness of little more than two feet. The shape of the hill is that of a truncated cone, the diameter of the summit being about one hundred yards. Round this flat summit is an immense number of small stones, piled up to form a rampart, and probably used in olden times both for defence and for attack on assaulters. Within the circle are many large masses of rocks, with small excavations on the tops of them, called "rock basins," formed, in all probability, by the natural decomposition of the granite, under the united action of the sun, rain, and wind. Detached granules of the stone, and others which may be loosened by the finger, are generally found at the bottom of these basins, and attest their most frequent origin, though others may have been partly formed by man, to supply his thirst or to perform his sacrifices.

The Kilmarth Rocks are a lofty range of half a mile in length, running east and west, about two miles northward from the Cheesewring, and in the parish of Linkinhorne, Cornwall. The westernmost pile, represented in the sketch, stands on the summit of this elevated ridge, and is in itself about twenty-eight feet high. It overhangs at least twelve or fifteen feet toward the north; and, when viewed from the east, appears so slightly based that a man or a strong gale might suffice to shove the