mine for this article; and though I was disappointed as to the fossil, I was highly gratified with the sight of several of the shells themselves in high preservation. This bivalve is only known to inhabit the Indian ocean, where it fixes itself to a zoophyte, known by the name Gorgonia. The curious foldings of the suture the one into the other, the alternate flutings or grooves, and the curved form of my specimen being much easier expressed by the pencil than by words, I have caused it to be drawn and engraved 2. 2 Notwithstanding the great care which was evidently bestowed by the author on the identification of his fossil shell, he was by no means so successful in the results of his research as he deserved to be: it is certainly not the analogue of the cock's comb oyster, the Mytilus Crista Galli of Linnæus and Ostrea Crista Galli of Lamarck; but belongs to an altogether different species which has not, so far at least as conchologists yet know, any living analogue. The figures given above, which are copied from those of the original edition, represent a shell of the species to which, on account of the strong ridge or keel along the middle of each of its valves, Lamarck gave the name of Ostrea carinata. It has repeatedly been figured, since the first publication of the Natural History of Selborne, as well in foreign as in English works: and, by a curious coincidence, in the Genera of Recent and Fossil Shells, by Mr. G. B. Sowerby, one plate contains representations both of this fossil (from a gigantic specimen) and of the cock's comb oyster, to which Gilbert White referred it. Though both are plaited oysters, the plaits or folds are disposed in a manner altogether dissimilar in the two shells in the cock's comb oyster they are in the longitudinal direction of the shell, which, moreover, is rounded in its general outline; in the keeled oyster they pass transversely on each side from a ridge which is continued along the middle of a considerably produced shell. The statement in the text, that it was obtained in the chalky fields, renders it necessary to caution the reader against regarding it as a chalk Cornua Ammonis are very common about this village3. As we were cutting an inclining path up The Hanger, the labourers found them frequently on that steep, just under the soil, in the chalk, and of a considerable size. In the lane above Well-head, in the way to Emshot, they abound in the bank in a darkish sort of marl; and are usually very small and soft: but in Clay's Pond, a little farther on, at the end of the pit, where the soil is dug out for manure, I have occasionally observed them of large dimensions, perhaps fourteen or sixteen inches in diameter. But as these did not consist of firm stone, but were formed of a kind of terra lapidosa, or hardened clay, as soon as they were exposed to the rains and frost they mouldered away. These seemed as if they were a very recent production *. In the chalk-pit, at the north-west end of The Hanger, large Nautili are sometimes observed. In the very thickest strata of our freestone, and at considerable depths, well-diggers often find large scallops, or Pectines, having both shells deeply striated, and ridged and furrowed alternately. They are highly impregnated with, if not wholly composed of, the stone of the quarry. fossil. The fields below the chalk downs at Selborne, though white in the appearance of their soil-a soil which thence derives its local appellation of white malm-belong in truth to the formation known to geologists by the confessedly and singularly inappropriate name of green sand. To the green sand formation the keeled oyster is peculiar: it appears even to be limited, as a fossil, to the upper green sand, the stratum on which the village of Selborne is built, and of which the immediately adjacent enclosures consist.-E. T. B. * There is a village in the west of England remarkable for the quantity it possesses of the "cornu ammonis." The name of it is Keynsham, between Bath and Bristol. "This has given rise to a fabulous legend, which says that St. Keyna, from whom the place takes its name, resided here in a solitary wood, full of venomous serpents, and her prayers converted them into stones, which still retain their shape."-See Espriella's Letters from England, vol. iii. p. 362.—MITFORD. They were probably casts of the ammonites rather than the shells themselves.-E. T. B. LETTER IV. TO THE SAME. As in a former letter the freestone of this place has been only mentioned incidentally, I shall here become more particular. This stone is in great request for hearth-stones, and the beds of ovens; and in lining of lime-kilns it turns to good account: for the workmen use sandy loam instead of mortar; the sand of which fluxes', and runs by the intense heat, and so cases over the whole face of the kiln with a strong vitrified coat like glass, that it is well preserved from injuries of weather, and endures thirty or forty years. When chiselled smooth, it makes elegant fronts for houses, equal in colour and grain to the Bath stone; and superior in one respect, that, when seasoned, it does not scale. Decent chimneypieces are worked from it of much closer and finer grain than Portland; and rooms are floored with it; but it proves rather too soft for this purpose. It is a freestone, cutting in all directions; yet has something of a grain parallel with the horizon, and therefore should not be surbedded, but laid in the same position that it grows in the quarry. On the ground abroad this firestone will not succeed for pavements, because, probably, some degree of saltness prevailing within it, the rain tears the slabs to pieces 3. Though this stone is too hard to be acted on by vinegar, yet both the white part, and even the blue rag, ferment strongly in mineral acids. Though the white stone will not bear 1 There may probably be also in the chalk itself, that is burnt for lime, a proportion of sand; for few chalks are so pure as to have none. "To surbed stone is to set it edgewise, contrary to the posture it had in the quarry," says Dr. Plot, Oxfordsh. p. 77. But surbedding does not succeed in our dry walls; neither do we use it so in ovens, though he says it is best for Teynton stone. 3 Firestone is full of salts, and has no sulphur: must be close-grained, and have no interstices. Nothing supports fire like salts; salt-stone perishes exposed to wet and frost.-Plot's Staff. p. 152. wet, yet in every quarry, at intervals, there are thin strata of blue rag, which resist rain and frost, and are excellent for pitching of stables, paths, and courts; and for building of dry walls against banks, a valuable species of fencing, much in use in this village; and for mending of roads. This rag is rugged and stubborn, and will not hew to a smooth face; but is very durable: yet, as these strata are shallow and lie deep, large quantities cannot be procured but at considerable expense. Among the blue rags turn up some blocks tinged with a stain of yellow, or rust colour, which seem to be nearly as lasting as the blue; and every now and then balls of a friable substance, like rust of iron, called rust balls. In Wolmer Forest I see but one sort of stone, called by the workmen sand, or forest, stone. This is generally of the colour of rusty iron, and might probably be worked as iron ore; is very hard and heavy, and of a firm compact texture, and composed of a small roundish crystalline grit, cemented together by a brown, terrene, ferruginous matter; will not cut without difficulty, nor easily strike fire with steel. Being often found in broad flat pieces, it makes good pavement for paths about houses, never becoming slippery in frost or rain; is excellent for dry walls; and is sometimes used in buildings. In many parts of that waste it lies scattered on the surface of the ground; but is dug on Weaver's Down, a vast hill on the eastern verge of that forest, where the pits are shallow, and the stratum thin. This stone is imperishable. From a notion of rendering their work the more elegant, and giving it a finish, masons chip this stone into small fragments about the size of the head of a large nail; and then stick the pieces into the wet mortar along the joints of their freestone walls: this embellishment carries an odd appearance, and has occasioned strangers sometimes to ask us pleasantly, "whether we fastened our walls together with tenpenny nails?" AMONG the singularities of this place, the two rocky hollow lanes, the one to Alton, and the other to the forest, deserve our attention. These roads, running through the malm lands, are, by the traffick of ages, and the fretting of water, worn down through the first stratum of our freestone, and partly through the second; so that they look more like water-courses than roads; and are bedded with naked rag for furlongs together. In many places they are reduced sixteen or eighteen feet beneath the level of the fields; and after floods, and in frosts, exhibit very grotesque and wild appearances, from the tangled roots that are twisted among the strata, and from the torrents rushing down their broken sides; and especially when those cascades are |