Most of the chalk-pits of the chalk-hill of Kent, from Dartford and Maram's Court Hill near Sevenoaks, to the white cliffs of Dover and Folkstone, are rich in extraneous fossils. One of the capital fossils of my own little collection came from the chalk-pit at Lenham. Great part of Mr. Lhwyd's collection, now in the Ashmolean Museum at Oxford, came from the stone-pits of Oxfordshire, especially from those of Stunsfield and Shotover. The black fissile slate which is found over veins of coal, and the brown nodules that occur in iron mines, which they call cat-heads, afford variety of fossil plants; vast numbers of which have been discovered in the coal mines of Somersetshire, Gloucestershire, Shropshire, and Glamorganshire. Many curious things have been found in the stone-pits of Northamptonshire, of which a very good account is given by Mr. Morton, in his Natural History of that county. Amongst the stone of that rock which skirts the Weald of Kent, I have found the cornu ammonis, from one inch to 18 in diameter, some of them squeezed almost flat; the mailed and paper nautilus, almost as large as the nautilus Græcorum; the trochus, four inches in diameter at the base; oysters of different sizes

sizes in the highest preservation, and amongst them the tree oyster; the pinna marina; the muscle; wood petrified and perforated by. sea-worms, as the piped waxen vein of Sheepy; the bucardites; the arca Noæ; the anomia lævis margine sinuato, anomia striata, pectines and pectunculi of various sizes, echinites spatagus, cordatus, pileatus, and fibularis, the cochlitæ in vast masses, and well preserved; with many others, of which I cannot here give a particular description: so fruitful may a single spot be found by one who examines it attentively for a long time, as my situation formerly in that part of Kent gave me an opportunity of doing.

The Lithophylacium of Mr. Lhwyd, reprinted within these few years at Oxford, and Dr. Woodward's Catalogues, now become exceedingly scarce, will give information to those who desire a more accurate acquaintance with the English fossils; and to these I must refer for farther satisfaction.

AN EXPLANATION OF THE FIGURES OF PLATE VII.

This Discourse on Fossils may fall into the hands of some readers, who are absolute

strangers

strangers to the kinds of bodies therein treated of; therefore I thought it necessary to add a few figures, each of them representing some one specimen of the several classes of figured fossils, nearly in the order in which they are laid down by Mr. Lhwyd in his Lithophylacium Britannicum; to which book, as the most convenient upon the subject, I must refer those who desire to see a greater variety of figures, with their explanations.

Fig. 1. Iceland crystal. A transparent body of a rhomboidal form; some specimens of which (but of an inferior sort) are found in England. This crystal has the peculiar property of producing a double refraction in the visual rays that pass through it, so that a single line drawn upon paper appears like two parallel lines.

Fig. 2. Selenites rhomboidalis. This is another transparent body, generally found in clay, and consisting of thin parallel plates, into which it is easily split. Sometimes it has ten sides, sometimes fourteen. It is nearly allied to talc, and to a glittering substance found in stone and sand, called mica.

Fig. 3. Fluor, or spar; commonly found in the joints and fissures of stone; much like some crystals in its form, and scarcely to be