The Quarterly journal of the Geological Society of London . ?^fVv^^Vlpv. Sb = Dactylioceras commune, = Polymorph ites Jupiter, Old Dalby. Diameter = 57 = 18 mm, secretion commenced in the region farthest removed from thesiphuncle. Partly formed septa, showing the same peculiarities,have also been noticed in Fol//morphites p(i)iter dOrhigny (fig. 6h). The formation of the septum in ammonites seems to have takenplace in the same manner as in living Nautilus. It has longbeen known i that in the latter the deposition of calcareousmattei- begins at the sides of the shell, and
The Quarterly journal of the Geological Society of London . ?^fVv^^Vlpv. Sb = Dactylioceras commune, = Polymorph ites Jupiter, Old Dalby. Diameter = 57 = 18 mm, secretion commenced in the region farthest removed from thesiphuncle. Partly formed septa, showing the same peculiarities,have also been noticed in Fol//morphites p(i)iter dOrhigny (fig. 6h). The formation of the septum in ammonites seems to have takenplace in the same manner as in living Nautilus. It has longbeen known i that in the latter the deposition of calcareousmattei- begins at the sides of the shell, and proceeds towards thesiphuncle. Willey (19U2) observed further that the secretion of aseptum was preceded by the formation of a conchiolin membrane,upon which the calcareous matter was deposited. The septa, just described for Dacti/lioceras and Foh/morphites, ^ F. A. Bather, Growth of Cephalopod Shells Geol. Mag. dec. 3, vol. iv1887) p. 447. j)2 3G PEOF, II. H. swiyyEKTOX AXD :NrE. A. E. TErEiiAX Tvol. Ixxui were complete in all sutrural details and, though only forme
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Keywords: ., bookcentury1800, bookdecade1840, booksubjectgeology, bookyear1845
