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contain the same in some very small, in others scarce or not at all visible".— But I flatter myself, that it will be found upon enquiry, that these are only circumstances, which are common to other testaceous bodies, that have been accidentally broken or decayed by time, when forsaken by their inhabitants. For no testaceous body can be formed without an inhabitant; nor does it appear to me, that any Belemnite was ever formed without an alveolus, or concamerated shell.
The conical cavity and its nucleus are always proportioned to the bulk of the Belemnite, but not to its length: some are four times longer in proportion to the alveolus than others. The apex of the conical cavity, where the alveolus is first formed, in some runs up about half the length of the whole Belemnite; in others not a sixth part of the whole [1]: but the aperture, or upper chamber [2] is equally proportionable to the bulk, or circumference of the Belemnite, of whatsover size or shape; and is the seat [3] or dwelling-place of the animal, that forms the Belemnite. In what manner this work is executed, I shall now endeavour to explain.
A considerable part of marine bodies, especially those of the testaceous tribe, are generally buried in mud or sand, except some few, which stick to rocks, &c as the limpets and periwincles; by which means we are prevented from making those remarks upon the several stages of their growth, which an accurate enquirer would desire. We must therefore have re-
