There are shell-fish which live at the bottom of the sea, and which are never cast on the shore; authors call them Pelogiæ, to distinguish them from the others which they call Litterales. It is to be supposed the cornu ammonis, and some other kinds that are only found in a petrified state, belong to the former, and that they were filled with the stony sediment in the very places they are found. There might also have been certain animals, whose species are perished, and of which number this shell-fish might be ranked. The extraordinary fossil bones found in Siberia, Canada, Ireland, and many other places, seem to confirm this conjecture, for no animal has hitherto been discovered to whom such bones could belong, as they are, for the most part, of an enormous size. These shells, according to Woodward, are met with from the top to the bottom of quarries, pits, and at the bottom of the deepest mines of Hungary. And Mr. Ray assures us, they are found a thousand feet deep in the rocks which border the isle of Calda, and in Pembrokeshire in England. Shells are not only found in a petrified state, at great depths, and at the tops of the highest mountains, but there are some met with in their natural condition, and which have the gloss, colours, and lightness of sea-shells; and to convince ourselves entirely of this matter, we have only to compare them with those found on the sea shores. A slight examination will prove that these fossil and petrified shells are the same as those of the sea; they are marked with the same articulations and in the glossopetri, and other teeth of fishes, which are sometimes found adhering to the jaw-bone, the teeth of the fish are remarked to be smooth and worn at the extremities, and that they have been made use of when the animals were alive. Almost every where on land we meet with fossil-shells, and of those of the same kind, some are small, others large, some young, others old; some imperfect, others extremely perfect and we likewise sometimes see the young ones adhering to the old. The shell-fish called _purpura_ has a long tongue, the extremity of which is bony, and so sharp, that it pierces the shells of other fish; by which means it draws nutriment from them. Shells pierced in this manner are frequently found in the earth, which is an incontestible proof that they formerly inclosed living fish, and existed in those parts where there were the Purpura.