cular surfaces, and of standing firmly on the ground, when, with its wings folded, it might crawl or hop like a bird. Restorations of the Pterodactyle may also be seen at the Crystal Palace, near the Hylæosaurus. The remains of fishes in the Wealden beds are frequent. The Ganoid Order (according to the arrangement of Agassiz) is represented by the Lepidotus. It was covered by angular and enamelled scales. The Ganoids occur principally in the older rocks; they are now represented by the fresh-water garpike of America, and the sturgeon of our

own seas.

The uniformity of the laws which has ever regulated the distribution of organic life is observable in the shells of the Wealden. However numerous the individuals found in our present lakes, rivers, or estuaries, the genera are but few. An instructive comparison may be made illustrating the prevalence of this law at the geological period under consideration, by placing side by side selected slabs of equal size of Kentish Rag and Sussex Marble. In the former may be counted, within a space of say three feet square, I shall not err in venturing to suggest the probable number of ten or twelve distinct species of marine shells. One would rarely find one third of that number in a slab of Sussex Marble of the same dimensions. But the individuals may be fairly expected far to exceed those in the Rag. The Sussex and Purbeck Marbles, so extensively used in church architecture late in the twelfth and in the thirteenth centuries, especially in the style designated Early English, are frequently made up of a fresh-water snail-Paludina (figure 1)— a genus which has its living representatives in our own lakes and ponds. To the sections of these Paludinæ, as cut by the mason, the marble owes its beauty. Other univalves, as Melanopsis, Melania, occur; also the bivalve genera, Cyrena and Cyclas. A small crustacean, Cypris (figure 2), is found in great abundance; a genus that has existed from the coal deposits to our own epoch. From their habit of annually casting off their carapace, or outward integument, myriads of their tiny exuvia or coverings are found throughout the clay beds. Among the shells, there remains to be noticed a small oyster, Ostrea distorta, which occurs in bands at Hythe, as I have myself noticed, and as had previously been elsewhere observed, which strongly confirms the estuary origin of the Wealden strata. Their presence

It is much to be regretted that the Sussex marble has fallen into disuse. Worked for chimney-pieces, it is equal to many native and imported marbles.

points to the occasional mixing of salt water with fresh, a condition favourable to their development, as a species inhabiting brackish water. At Hythe these bands appear in the uppermost beds, and therefore towards the close of the Wealden Epoch, when the sea was about to obtain the mastery; we may fairly infer this, for there is a line of junction above which the freshwater shells are replaced by those exclusively marine-those of the Lower Green Sand. The sea now rolled where previously a river flowed. If one may be permitted to speculate, it may be inferred that the final submergence of the Weald under the sea was tranquil, and just such as would occur by a gradual subsidence of its bed. The mineralogical character of the Weald clay differs so slightly from that of the Atherfield, that the line of of junction can be ascertained only by fossil evidence.

I may here venture to allude to the value of such evidence in distinguishing the fresh-water from the marine beds. I required a strong stiff clay for the operation of puddling, and commenced by procuring it from the Weald clay. The presence of concretions of clay iron ore in this bed are so frequent that it rendered the process all but impracticable. I knew that in the Atherfield (marine) clay these nodules did not occur. Removing the site of my excavation a few feet higher up, to the Atherfield, which is above the Wealden, I dug until I found marine bivalves (Panopæa), and obtained a perfectly homogeneous clay free from nodules or other hindrances, admirably adapted for the purpose for which it was required.

Such were the conditions under which the Wealden was deposited. Evidences are not wanting to lead to the inference that, notwithstanding its great thickness, its bed was during the period of deposition gradually sinking. At Hastings and elsewhere ripple-marked sand stones abound, and Sir Charles Lyell figures a slab from Stammerham, Sussex, which indicates that its exposure to the air caused it to crack before the last layer was thrown down. It is interesting to trace the rippling action of a breeze upon shallow water in ages so remote. It is impossible for me in these limits to enumerate the further evidences indicative of the gradual subsidence of the Wealden during its deposit; and I must therefore refer the reader to the Anniversary Address of Sir Charles Lyell to the Geological Society, 1850, for a discussion of the elevation and depression of land.

* Geological Journal, vol. vi., p. 2.

*

Overlying the fresh-water Wealden strata are the beds of that member of the cretaceous formation designated the Lower Green Sand. It forms generally, and particularly in the eastern part of Kent, a line of low hills, its escarpment overlooking the valley of the Weald, and as seen from the summit of the loftier chalk, it presents a table-land spread out in gentle undulations at its base.

The Lower Green Sand has in Kent four well marked subdivisions, designated as follows:

The Atherfield clay derives its name from the spot where it may most conveniently be studied, Atherfield Point, in the Isle of Wight; it offers no natural section in Kent. Its marine origin is revealed by its organic remains. The few opportunities which have offered in the neighbourhood of Hythe, when artificially pierced, have afforded Ammonites Deshayesii, Pinna sulcifera, &c. I believe that under proper manipulation it would prove superior to the clays either of the Weald or the Gault, in the hands of the potter. It presents no distinguishable feature in the landscape, forming merely a narrow belt on the slope of the Quarry Hills, with the debris of which it is much mixed at the surface. I have observed it to produce wheat and other crops superior to those of the underlying Weald; and some of our finest oaks rejoice in its fertility. An artificial section is exposed in the cutting of the South-Eastern Railway at the Smceth station, where the overlying Kentish Rag may be noticed; and it crops out at Seabrook immediately under the Hythe beds, which have next to be considered.

These beds first emerge from the sea level between Sandgate and Folkestone, rising gradually along the base of Shorncliffe, till they form the escarpment above the town of Hythe. The admirable artificial section afforded in the quarries at that place has given this subdivision its title of the "Hythe beds." They, as also the Rag beds at Maidstone, have afforded a rich harvest to the paleontologist. The well-known specimen of the Iguanodon preserved in the British Museum was obtained by Mr. Bensted, of Maidstone, in the quarries near that town.