The

are calcareous, not siliceous like those of Portland. wood is more or less traversed by veins and filaments of pyrites, which impart a beautiful appearance to polished specimens of the stems. Slices rendered transparent by Canada balsam, exhibit under the microscope, in the transverse sections, the cellular tissue as a reticulation of polygonal meshes; and in the radial, the ducts or glands characteristic of the coniferæ, and arranged in alternate rows as in the araucaria or Norfolk Island Pine.* The annular lines of growth are often very distinct; I have traced from thirty to forty on some of the stems. These circles are of unequal thickness, and therefore indicate a variation from year to year in the climate of the country in which they grew. They are, too, as small as in the slow growing pines and firs of England. Many of the stems exhibit an obliquity in the annular lines, proving that they grew in situations which exposed the trees to prevailing currents of wind from a particular quarter, and caused them to incline in the opposite direction. I have discovered no vestiges either of the foliage or fruit. It is remarkable that coniferous wood occurs but sparingly, if at all, in the Wealden deposits of the south-east of England; but drifted stems and branches of pines of the araucarian type, are common in some of the upper beds of the greensand, and are occasionally met with in chalk flints.t

Such is a brief description of the accumulation of fossil trees at Brook Point, which evidently originated in a raft composed of a prostrate pine-forest, transported from a distance by the river which flowed through the country whence the Wealden deposits were derived, and became submerged in the sand and mud of the delta, burying with it the bones of reptiles, mussel-shells, and other extraneous bodies it had gathered in its course.

* See "Medals of Creation," vol. i. p. 71.

"Medals," vol. i. p. 168.

In the strata that overlie the fossil forest, thin interrupted seams of lignite,* and masses of the same substance invested with crystals of brilliant pyrites, are every where abundant; and beautiful and instructive specimens may be obtained. In the clays for several hundred yards both to the east and west of Brook Point, bones of the Wealden reptiles are numerous; with these are associated large mussel-shells (Pl. VI. fig. 1), and lignite. To the east of Brook Bay is Brixton Bay; and along this line of coast, as far as Atherfield, similar organic remains are continually met with after the high tides of the early spring. I have not examined the cliffs further to the eastward, and must refer to Dr. Fitton's Memoir for a particular enumeration of every important stratum, along the southern coast of the Isle of Wight. My attention has always been so much engrossed by the interesting phenomena observable in Brook Bay, which is at all times easy of access, that I have had neither leisure nor inclination to extend my researches to the east of the point above mentioned. Dr. Fitton states that in the cliff at "Tiepit, and thence to Shepherd's Chine, and within that chine and Cowlease Chine, the Wealden clay and its passage to the sands beneath, are better displayed than in any other localities."‡

* LIGNITE, &C. For an account of the changes by which vegetable substances are converted into lignite, coal, &c., see “Medals of Creation," vol. i. chap. 5.

Unfortunately these specimens generally fall to pieces after a few months, in consequence of the decomposition of the pyrites with which they are permeated.

"Geol. Trans." vol. iv. p. 198.

CHAPTER X.

ORGANIC REMAINS OF THE WEALDEN-FOSSIL VEGETABLES ENDOGENITES EROSA-CYCADEOUS PLANTS-CLATHRARIA LYELLII -FOSSIL SHELLS-UNIO VALDENSIS-FOSSIL CYPRIDES-FOSSIL FISHES.

FOSSILS OF THE WEALDEN.-The Wealden strata of the Isle of Wight have afforded examples of the most characteristic organic remains that have been discovered in this formation in other parts of England. They have yielded five or more genera of terrestrial plants; of which one belongs to the Pines, several to the Cycadeæ, and two or three to the Ferns several species of river-shells, of the genera Unio, Paludina, Potamides, Cyclas, &c.; and of the small crustaceans, the Cyprides. Fishes allied to the Bony-pike and the Sharks occur, and bones of seven or eight species of terrestrial saurian reptiles, and of two or three genera of Chelonians.

FOSSIL VEGETABLES.- Our description of the fossil forest of Brook Point entered so fully into the character of the coniferous trees of the Wealden, that it is unnecessary to enlarge upon that subject. A great proportion of the lignite in the laminated sands and clays forming those cliffs, is undoubtedly the bark of the mature trees, and the wood of the young plants, in a carbonized state.

But the coaly particles disseminated through the strata have probably, in a great measure, originated from the foliage of two elegant extinct species of ferns, that abound in some parts of the Wealden of Sussex, and of which a few recognisable specimens have been discovered in the Isle of Wight.

BROOK POINT.

Fig. 1.-Portion of three leaflets, magnified, to show the reticulations of the veins. 2. Part of a stem, with leaves.

FOSSIL FERNS.-Entire layers of the sandstone, grit, and shale, in Tilgate Forest, are so full of carbonaceous matter as to acquire a dark mottled colour, and this detritus is composed of minute particles of the leaves and stems of ferns, that have been ground to pieces by agitation in water loaded with sand and mud. One of these plants (Sphenopteris Mantelli, "Wonders of Geology," p. 370) is characterised by its slender wedge-shaped leaflets. The other fern (Lonchopteris Mantelli, lign. 21) is the species already mentioned as occurring in the greensand of Atherfield and Shanklin. It is distinguished by its long and many-times pinnated leaves, and the reticulated disposition of the secondary veins that spring from the mid-rib of the leaflets.

ENDOGENITES EROSA.-In the strata of Tilgate Forest, and in the sands at Hastings, numerous fragments of the stems of a remarkable monocotyledonous (?) plant occur,

and are mentioned in my Fossils of the South Downs, and figured in the Fossils of Tilgate Forest, &c. These stems are of various forms; some are cylindrical, and tapering at both ends; and others are flattened, and of a clavated shape, like some of the Cacti and Euphorbia; the specimens are from a few inches to seven or eight feet long, and the largest from twenty to thirty inches in circumference. When imbedded in the strata, a thick coat of lignite surrounds the stem; but this soon becomes friable, and falls off after exposure to the air. The constituent substance of the stems is a grey, compact, subcrystalline sandstone, and the external surface is traversed by fine semicircular grooves and deep tubular furrows, lined with minute quartz crystals; a transverse section exhibits the surface covered by small pores, and a few large openings, the sections of the tubes. From the eroded appearance of the surface of the specimens, when deprived of their carbonaceous investment, the name Endogenites erosa, was given to this fossil plant by Messrs. Stokes and Webb, who described it from my specimens, in the "Geological Transactions," vol. i., second series. Dr. Fitton* subsequently described and figured a series of interesting specimens observed by him in the strata at Hastings. In transverse slices of these fossils, obscure indications of circular bundles of vascular tissue were detected, but (as in all my specimens from Tilgate Forest) very few vestiges of organic structure were apparent; the cavities exposed in the sections being not the vessels themselves, but the hollows left by their decay.† The occurrence of this fossil plant in the Wealden of the Isle of Wight has only recently been discovered. Among the waterworn fossils which I collected from the shingle, on my last visit to Brook Point, was a rounded,

* "Geol. Trans." vol. iv. p. 172.

Dr. Fitton has given magnified figures of the sections in his pl. xx.