The author describes, in the present paper, specimens of Belemnite, discovered in the Oxford-clay at Christian Malford, Wilts, and which are remarkable for the preservation of many of the soft parts of the animal. After alluding to the various opinions promulgated by different authors respecting the nature and affinities of this extinct animal, he adverts more especially to the discovery of the ink-bag of the Belemnite, which was published in the Zoological Transactions, vol. ii., and in the Cyclopaedia of Anatomy and Physiology (Art. Cephalopoda). This discovery led him, on the strength of deductions from the physiological relations of this organ, to remove the Belemnite from the
Polythalamacea
of De Blainville, and place it in the higher order of the naked Cephalopods. The structure of the shell is next discussed, and the spathose dart, or guard, is proved to be the result of original organization, both by its microscopic structure and by the fact that the chambers of the phragmocone have not been infiltrated by mineral substance in any of the specimens described: the name
phragmocone
being applied to the chambered and siphonated conical division of the compound shell of the Belemnite; and the term
alveolus
being restricted, in the present paper, to the socket or cavity at the base of the guard, in which the phragmocone is lodged. A detailed description is given of the sheath of the phragmocone and of the structure of the chambers. The state of preservation of the present specimens has enabled the author to describe the form and extent of the mantle—its continuation over the exterior of the shell, and the arrangement of its muscular fibres. The animal is provided with two lateral fins of a semi-oval figure, which are attached to the middle of the mantle, in advance of the spathose dart.
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