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The Ammonite Siphuncle

Published online by Cambridge University Press:  01 May 2009

A. E. Trueman
A. E. Trueman
Affiliation:
University College, Cardiff.
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Extract

It is well known that the chambers of Cephalopod shells are connected by an organ called the siphuncle, which passes through the septa by the septal necks. Many investigators who have studied these shells have made careful observations on the siphuncle, hoping thereby to throw light on its functions. Such workers as Branco, Blake, Zittel, and Owen, among many others, have written on this problem, while more recently an elaborate study of the structure and constitution of the siphuncle has been made by Grandjean, who gives a detailed account of the organs associated with it. Among the many points established by Grandjean's work, not the least interesting is the fact that the siphuncular tube of Ammonites and Belemnites is composed of calcium phosphate, and not, as had previously been stated, of calcium carbonate. But in spite of Grandjean's careful examination of the less obvious characters of the siphuncle, it appears that certain facts, much more easily observed, have hitherto been overlooked.

Type
Original Articles
Information
Geological Magazine , Volume 57 , Issue 1 , January 1920 , pp. 26 - 32
Copyright
Copyright © Cambridge University Press 1920

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References

page 26 note 1 Grandjean, F. “Le Siphon des Ammonites et des Belemnites”: Bull. Soc. Géol., France, ser. iv, vol. x, 1910, p. 496.Google Scholar

page 26 note 2 This further point of resemblance between Ammonites and Belemnites is interesting in view of Dr. W. D. Lang's recent suggestion concerning their classification (Proc. Geol. Assoc., vol. xxx, p. 59).

page 27 note 1 Further, asymmetry is of extremely rare occurrence in such keeled ammonites. See Swinnerton, & Trueman, , Quart. Journ. Geol. Soc., vol. lxxiii, 1918, p. 54.Google Scholar

page 29 note 1 Mr. F. F. Miskin, F.G.S., kindly examined a number of these Ammonites, and proved that this white material was calcium phosphate, and therefore represents the siphuncular tube.

page 30 note 1 In Oppel, Palæont. Mitt. Mus. d. k. bayer. Staates, Bd. ii, 1868, pp. 79–80. I have to thank Mr. F. T. Ingham, B.Sc., for supplying particulars of this paper.

page 30 note 2 Op. cit., p. 502.Google Scholar

page 31 note 1 Blake, J. F., British Fossil Cephalopods, vol. i, 1882, p. 39.Google Scholar

page 31 note 2 Zittel, K. v., Handbuch der Palaeont., Bd. ii, pt. i, p. 348.Google Scholar

page 31 note 3 Wright, T., Monograph of Lias Ammonites, Palæont. Soc., 1878–1886, p. 174.Google Scholar

page 31 note 4 The total weight of the ammonite animal and its gas-filled shell was probably not very different from the weight of water it displaced. See DrWilley, F., The Pearly Nautilus, 1902, p. 747.Google Scholar

page 31 note 5 Spath, L. F., “Notes on Ammonites”: Geol. Mag., Vol. LVI, 1919, p. 30.Google Scholar

page 31 note 6 Smith, E. A., “Note on the Pearly Nautilus”: Journ. Conch., 10. 1887.Google Scholar

page 31 note 7 Op. cit., p. 760.Google Scholar

page 32 note 1 This would be equally true of Ammonites, in which Mr. Spath suggests that the complex lobes and saddles served as an attachment. See also DrLang, W. D., “The Evolution of Ammonites”: Proc. Geol. Assoc., vol. xxx, 1919, p. 63.Google Scholar

page 32 note 2 Foord, H. O., Catalogue of Fossil Cephalopods in Brit. Mus., vol. i. 1888, pp. 10–11.Google Scholar

page 32 note 3 Woodward, H., Pop. Sci. Review, vol. xi, 1872, p. 113.Google Scholar