Page:Geology and Mineralogy considered with reference to Natural Theology, 1837, volume 1.djvu/274

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name of Nautilus Sypho has been applied to a very curious and beautiful chambered shell found in the Tertiary strata at Dax, near Bourdeaux; and that of Nautilus Zic Zac to a cognate shell from the London clay. (See Pl. 43, Figs. 1, 2, 3, 4.)

These fossil shells present certain deviations from the ordinary characters of the genus Nautilus, whereby they in some degree partake of the structure of an Ammonite.

These deviations involve a series of compensations and peculiar contrivances, in order to render the shell efficient in its double office of acting as a float, and also as a defence and chamber of residence to the animal by which it was constructed.

Some details of these contrivances, relating to the Nautilus Sypho will be found in the subjoined note.