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Memoir on the Pearly Nautilus by R. Owen 1832.

p.31. Sepia shows affinity to Nautilus in its Laminate shell - in extremities of branchiæ being unattached & in a rudimentay accessory branchiæ — Hence Sepia closest to the tetra-branchiate & lowest form of Cephalopods. See d'Orbigny's memoir —

p. 39. Nautilus has an inferiorly constructed brain & more simple eye, than in the dibranchiate group

p 50. Nautilus is an osculent form between cephalopods & gasteropods, (though belonging to former clearly) Pteropods do not come between. It is interesting the tetra-branchiate including Nautilus Ammonite, Belemnites Spirula (?) (Over &c & being older than the other recent genera — see Owens paper on Belemnite; does he yet Consider Belemnite as tetra-branchiate—

over

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Owen on Belemnite p. 82. It seems that in 1836 — He classed Spirula & Belemnite with the Dibranchiate Cephalopods & his first examination of Belemnite leads still further to this. Considers Belemnite as intermediate between Spirula & Sepia

Owen, Richard. 1832. Memoir on the pearly nautilus (Nautilus pompilius, Linn.); with illustrations of its external form and internal structure. London: for Royal College of Surgeons.

Owen, Richard. 1844. A description of certain Belemnites, preserved, with a great proportion of their soft parts, in the Oxford clay, at Christian-Malford, Wilts. Philosophical Transactions of the Royal Society of London 3: 65-85, 5 pls. [Darwin Pamphlet Collection Quarto 15] PDF