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 them in a much more perfect slate than the former, with the alveolus in many of them; but that part is commonly crushed by the incumbent matter.

The siphunculus of the Belemnite is always upon the verge of the chamber, or cell; and in the siphunculus is a little gutt or ductus, proceeding from the body of the animal, by dilating or contracting of which the animal, it should seem, may go out or into its cell at pleasure. This is the only stay, which the animal has to secure its retreat: but I cannot agree with the learned doctor Hooke, that the gut or ductus passes through all the cells to the end of the spiral cone, either in this shell or the nautilus. His discovering of a spiramentum in the center of the latter was merely conjectural; for the ends of the spiral cone of concamerated shells are shut up in the same manner with those of the turbinated kind: and it is common for all turbinated shell-fish, as they increase in bulk, and enlarge their shells, to leave their bottom or first-formed convolutions. Therefore I make no doubt but the same is done by the concamerated tribe; for if the gut go through only one or two valves, it will be a sufficient stay to the animal, and, being contracted or dilated, will serve all the purposes above mentioned. How far this is practicable by our little inhabitant, cannot absolutely be determined; but if it be constantly fixed by the gut to the siphunculus, it has a surprising power of contracting and dilating its body, to extend so far as the bottom or point of the Belemnite,

Rh