^{page 27 note 1} Quart. Journ. Geol. Soc., vol. lxxiii, pt. i, pp. 26–58, pls. ii–iv, 1917.Google Scholar

^{page 28 note 1} Handbuch d. Pal., vol. i, 2, pp. 332, etc., 1881–5.Google Scholar

^{page 28 note 2} “Form u. Bau d. Ammon.-Sept., etc.”: Jahresb. Niedersächs. Geol. Ver., vol. iv, pp. 221–2, 1911.Google Scholar

^{page 29 note 1} The specimen used by Swinnerton and Trueman for their series of septal sections (fig. 13 on p. 46) shows the small terminal leaflets of the ibex group.

^{page 29 note 2} Pictet (Traité de Paléont., p. 669) pointed out already in 1854 that the inflated “varieties” of a species often differed from the compressed ones in the number of the accessory lobes, and that modification of the umbilicus produced the same result.

^{page 29 note 3} “Etude sur les Cardioceratidés de Dives, etc”: Mém. No. 45, Soc. Géol. France, Pal., i, 19, fasc. 2, p. 14.Google Scholar

^{page 29 note 4} Additional work on the various features of the suture-line has demonstrated to the writer the impossibility of basing the separation of genera which other characters and especially geological occurrence would appear to connect (in this case Tragophylloceras and Rhacophyllites) on the comparatively insignificant difference in the endings of the external saddle.

^{page 30 note 1} “Ammonitiden des Norddeutschen Neocom.”: Abh. Preuss. Geol. Landesanstalt, N.F., Heft xxiv, p. 393, pl. xxxv, fig. 13Google Scholar.

^{page 30 note 2} Ibid., p. 398, pl. liii, figs. 11, 13, 14.

^{page 30 note 3} See Smith, E. A., “Note on the Pearly Nautilus,” Journ. Conch., 10, 1887Google Scholar; and Foord, , Cat. Foss. Ceph. Brit. Mus. (Nat. Hist.), pt. i, pp. xi, xii, 1888.Google Scholar

^{page 30 note 4} Diener, , “Lebensweise u. Verbreitung d. Ammoniten”: N. Jahrb. Miner., etc., ii, pp. 67–89, 1912.Google Scholar

^{page 30 note 5} “Vererbungsgesetze und ihre Anwendung auf den Menschen”: Darwinist. Schriften, I, vol. xviii, p. 22 (214), 1893.Google Scholar

^{page 31 note 1} In Zittel-Eastman, , Text-book of Pal., 2nd ed., vol. i, p. 673, 1913.Google Scholar

^{page 31 note 2} Menzel, , Zeitschr. Deutsch. Geol. Ges., vol. liv, p. 90, 1902.Google Scholar

^{page 31 note 3} Blake (in Great Oolite Mollusca, Mon. Pal. Soc. vol.), from the occurrence of this genus in the southern part only of the Cornbrash outcrop in England, concluded that it was dependent on the presence of the Great Oolite Series below, of whose fauna it was a relic. Compared with the almost universal distribution of the genus Macrocephalites, this restriction of Clydoniceras is interesting and shows that, like many modern marine organisms, certain Ammonite genera were undoubtedly strictly limited in their horizontal distribution. In aberrant or benthonic types, of course, like the Oxynoticeras derivative “Ægoceras” Slatteri, Wright, or Nipponites, the local restriction might be expected, more than in active swimmers.

^{page 31 note 4} Tornquist, , “Proplanuliten a. d. Westeuropäischen Jura”: Zeit. Deutsch. Geol. Ges., vol. xlvi, 1894Google Scholar; also “Die degenerierten Perisphinctiden d. Kimmeridge v. Le Havre”: Abh. Schweiz. Pal. Ges., vol. xxiii, 1896.Google Scholar

^{page 32 note 1} Op. cit., p. 42.

^{page 32 note 2} Ibid., p. 39.

^{page 32 note 3} Diener, (“Lebensweise u. Verbreitung d. Ammoniten”: N. Jahrb. Miner., etc., ii, p. 69, 1912Google Scholar) says that Nautilus lives chiefly crawling, but can swim well and quickly, and has also been found attached to the bottom, which “shows that its present mode of life is little stable yet”. Diener, therefore, does not agree with Dollo, (“Les Cephalop. adaptés à la vie nect. second. et à la vie benthique tertiaire”: Zool. Jb. Spengel. Festschr., Suppl., xv, 1, p. 111, 1912)Google Scholar, who ascribes a primarily benthonic mode of life to Nautilus, the “type of the ancient Cephalopod with functional, external shell”.

^{page 32 note 4} N. Jahrb. Miner., etc., ii, p. 169, 1913 (in review of Renz).Google Scholar

^{page 32 note 5} Geschichte der Erde und des Lebens, 1908, p. 451.Google Scholar

^{page 32 note 6} Haug, , Traité de Géologie, vol. ii, fasc. ii, p. 1166, 1908–1911.Google Scholar

^{page 33 note 1} Pia, J. v., Jahrb, N.. Miner., etc., i, p. 169, 1914, in review of Mr. Buckman's Yorkshire Type Ammonites.Google Scholar

^{page 33 note 2} In Zittel-Eastman, , Text-book of Pal., vol. i, p. 544, 1900.Google Scholar

^{page 33 note 3} “The Evolution of the Cretaceous Asteroidea”: Phil. Trans. Roy. Soc. Lond., ser. B, vol. 204, pp. 156–7, 1913.Google Scholar

^{page 33 note 4} Allen, Joel A., “The Influence of Physical Conditions in the Genesis of Species”: Smithson. Inst. Ann. Rep., 1905, p. 401.Google Scholar

^{page 34 note 1} Op. cit., 1912, p. 79. Frech, “Neue Cephalopoden a. d. Buchensteiner, Wengener, and Raibler Schichten d. südl. Bakony”: Res. Wiss. Erf. Balatonsees. Pal. Anh. z. Teil i d. Bd. i, p. 72 (quoted by Diener), expresses similar views.

^{page 34 note 2} The local restriction and numerical insignificance of this “goniatitic” form compared with its normal contemporaries and the flourishing Scaphites and Turrilites shows the incompleteness of the “cycle”.

^{page 34 note 3} Wurm, A., “Beitr. Kenntn. Iberisch-Balearischen Triasprovinz”: Verh. Naturhist.-mediz. Ver. Heidelberg, vol. xii, 4, 1913.Google Scholar This fauna is even more reduced than that of St. Cassian, which it resembles.

^{page 34 note 4} Leriche, M., “Sur la présence du genre Metoicoceras, Hyatt, dans la Craie du Nord de la France, etc”: Ann. Soc. Géol. Nord, vol. xxxiv, pp. 120–4, 1905.Google Scholar