illustrated by exquisite engravings-See Organic Remains, vol. II. p. 173.

The great Oolite.-In the great mass of this rock, perfect organic remains are rare, from the comminution which they seem to have undergone. Many small turbinated shells, like those of the forest-marble, occur here in the stone, and a bed containing numerous madrepores, several of which appear to be identical with those of the coral rag, forms a part of the series. Most of the fossils of the subjacent clay are common to the upper beds of the oolite,

VERTEBRAL ANIMALS.

Mammalia.-The calca

reous slate of Stonesfield presents bones, believed by M. Cuvier to belong to a species of Didelphys, or Opossum tribe. They are absolutely imbedded in the slate, along with various marine remains, and could not have been subsequenly introduced into its fissures. We have here therefore an unparalleled instance of the occurrence of animals of such an order, in strata deposited long before the superior or tertiary rocks, which are the ordinary mineral repositories of the exuviæ of the quadru peds buried so long before the flood.

OVIPAROUS QUADRUPEDS. Sauri.-A well characterised crocodile, but of a species distinct both from all those now known alive, as also from the extinct sauri of Germany, and from one at least of the French fossil species, has been dug up at Gibraltar near Oxford, and is now in the collection of that university. It was taken from a bed towards the upper part of this oolitic system, probably the Cornbrash.

CROCODILES CRUSHED TO DEATH.

259

An immense animal, the megalosaurus, already described, as resembling the monitor, occurs at Stonesfield in the calcareous slate. This animal bears a considerable resemblance also to the Lacerta gigantea found in Bavaria and described by Sommering in the Munich Transactions of 1816. A translation of his memoir is published in the Annals of Philosophy for September 1821. Ammonites were found in the vicinity of this last saurian animal, as is universally the case in all the known instances of fossil crocodiles, gavials, and lacertæ. The compressed and distorted form of the head and the marks of violence apparent in many places, ought to be noticed, since they indicate some great external force to which either the animal itself at its death, or its skeleton must have been subjected since; appearances common also to the crocodilus priscus. What a power of pressure must have been exerted not only to flatten the conical head, but even to force out and break the teeth, as has happened to the Bavarian fossil! "If I may be permitted to decide," says M. Sommering, "from my own anatomical and pathological knowledge, I should say that this compression of the head was not effected during the dry, friable, and brittle skeleton state; since in such a case, owing to the equal force, the upper jaw would have been broken in another direction; or at least would not have been so perfect, as it is now on the left side. The injury appears to have been rather inflicted on the living animal when the periosteum and top of the head could hold together the fragments of the bones, notwithstanding their crushed condition.

Hence it appears to me a subject well worthy attentive examination, why it happens in all the fossil animals of antiquity, except some later ones discovered in a lighter soil, that the heads in particular are not only crushed, but at the same time dislocated in their parts. How dreadfully shattered for instance are the fragments of the head and jaw discovered at Maestricht, the jaw of the Vicentine animal, the head of the specimen belonging to M. Spener, the heads of the palæotherium and anoplotherium found at Montmartre, and the head of the crocodilus priscus !"

TESTUDINES.-Remains of two or three species of tortoise occur in the Stonesfield calcareous slate. FISHES.-Teeth, palates, and vertebræ of fishes of several varieties are found both in the Stonesfield slate and in the Forest-marble of Atford near Bath: the same varieties belong to both places.

BIRDS.-Leg and thigh bones, apparently of birds, are imbedded in this calcareous slate.

INSECTS.-Coleoptera. Specimens pronounced by Dr. Leach to be decidedly the Elytra of Coleopterous insects occur in the Stonesfield slate. Two or three different species have been noted.

CRUSTACEA.-Two or three varieties of the crab or lobster tribe occur also in the Stonesfield slate.

All these organic remains are intimately associated with the shells which characterise this portion of the oolitic system, and cannot therefore be considered as a local, overlying, and recent deposit of animal bones. In the same beds, are found several varieties of shells, particularly a small studded tri

EX TENT OF THESE FORMATIONS IN ENGLAND. 261

gonia, and several vegetables, principally flags, ferns, and mosses.

TESTACEA. Multilocular Univalves.

These are the same genera for the Cornbrash, Forest marble, and clay over the oolite, as already given for the inferior oolite. For the species we refer to Mr. Conybeare's tabular list, Geology, p. 210. The same reference must be made as to the echinites, encrinites, and madrepores.

Irregular cylindrical branches often occur in all these beds originating apparently from Alcyoniæ; and in the great oolite there are well characterised fragments of these zoophytes, exhibiting distinctly their cellular and spongy texture. See Chalk Fossils.

Fossil wood is prevalent among all these beds, and especially in the Forest marble. In the Stonesfield calcareous slate, many beautiful vegetable impressions occur of ferns, flags, and mosses, analogous to those of the coal formation.

Range and extent.-The formations from the great oolite to the cornbrash inclusively constitute the mass of a well defined range of hills which run across the island in a diagonal direction from Yorkshire to Dorsetshire, and equal or surpass the great chain of the chalk hills in continuity, elevation, and extent. Mr. Smith has given the appropriate name of the Stonebrash hills to this range, from the stony fragments that are mixed with the surface soil. The Cornbrash usually forms the first acclivity of these hills where they begin to rise from the valley occupied by the Oxford clay, which accompanies them on the east and south-east; the Forest marble and calcareous slate advance still farther in the

ascent; the great oolite emerging from beneath them, forms their most elevated region and brow; and finally the subjacent beds, associated with the inferior oolite, already described, are displayed in the western slope and escarpment of these hills. The plains at their foot, are occupied by the lias. To the above general arrangement, there are a few exceptions caused probably by aqueous denudation.

Near Frome the horizontal beds of the oolitic series abut abruptly against the steep strata of the mountain limestone, connected with the lofty chain of Mendip, which here begins to rise. A sketch in Geol. of Eng. p. 226, explains how beds of such distant geological epochs as mountain limestone and oolite, come into immediate contact, in consequence of the difference of inclination through which their planes cut each other.

We have stated that this system passes across the island in a nearly continuous range of hills. Sometimes, the whole escarpment of these hills is formed by the inferior oolite, while the main oolite constitutes a slight upper terrace ranging at a distance inland. Crossing the Humber through Lincolnshire, the hills are low; they acquire more height in the counties of Rutland, Northampton, and Oxford, but the highest points in the formation are the summits rising near the edge of the escarpment (as Arbury and Epwell hills) which belong entirely to the inferior sands, the main oolite lying considerably to the south-east. In Gloucestershire, however, the great oolite always crowns the brow of the escarpment, and reaches its greatest height. The loftiest point of these hills is Cleevehill near