Page:Geology and Mineralogy considered with reference to Natural Theology, 1837, volume 1.djvu/242

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I must enter at some length into the natural history of these shells, because the conclusions to which I have been led, by a long and careful investigation of fossil species, are at variance with those of Cuvier and Lamarck, as to the fact of Ammonites being external shells, and also with the prevailing opinions as to the action of the siphon and air chambers, both in Ammonites and Nautili.

The Nautilus not only exists at present in our tropical seas, but is one of those genera which occur in a fossil state in formations of every age; and the molluscous inhabitants of these shells, having been among the earliest occupants of the ancient deep, have maintained their place through all the changes that the tenants of the ocean have undergone.

The recent publication of Mr. R. Owen's excellent Memoir on the Pearly Nautilus, (Nautilus Pompilius Lin.) 1832, affords the Erst scientific description ever given of the animal by which this long-known shell is constructed. This Memoir is therefore of high importance, in its relation to

ther the Sepia found within this shell be really the constructor of it, or a parasitic intruder into a shell formed by some other animal not yet discovered. Mr. Broderip, Mr. Gray, and Mr. G. Sowerby, are of opinion, that this shell is constructed by an animal allied to Carinaria.