Page:Geology and Mineralogy considered with reference to Natural Theology, 1837, volume 1.djvu/289

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Comparing the shell of Belemnite, with that of Nautilus, we find the agreement of all their most important parts to be nearly complete; and the same analogies might be traced through the other genera of chambered shells.

strata was deposited upon them, in a soft and fmuid state. (See Allan's Paper on Belemnite, Trans. Royal Soc. Edin., and Miller's Paper, Geol. Trans. Lond, 1826, p. 53.)

Thus of the millions of Belemnites which crowd the Secondary formations, only the fibro-calcareous sheath and chambered alveoli are usually preserved; whilst in certain shale beds this sheath and shell have sometimes entirely disappeared, and the horny or nacreous sheath or ink-bag alone remain. See Pl. 44″, Fig. 1, 2, 3, 4, 5, 6, 7, 8. In the rare case, Pl. 44′, Fig. 7, which has afforded the clue to this hitherto unexplained enigma, we have all the three essential parts of a Belemnite preserved in their respective places nearly entire. The ink-bag (c) is placed within the anterior horny cup (e, e', e″;) and the chambered alveolus, (b b') within the hollow cone of the posterior fibro-calcareous shell, or common Belemnite.