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On Jurassic Ammonites from East Africa, collected by Prof. J. W. Gregory

Published online by Cambridge University Press:  01 May 2009

L. F. Spath
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Extract

Description.—This specimen is characterized by a subrectangular whorl-section with depressed venter, which is peculiar to Fontannes's group of “Phylloceras” tortisulcatum. The greatest thickness of the whorls is near the umbilical margin, but the sides are almost parallel and the ventral area is evenly convex, not flattened. The ratio of height to thickness is about 7: 6, as compared with 4: 3 in Sowerbyceras tortisulcatum, according to Pompeckj, and with 8: 7 at most in S. protortisulcatum Pompeckj sp. The umbilicus is comparatively large and deep; its walls are rounded and not abrupt. There are about four constrictions to the whorl, beginning as conspicuous grooves with a forward bend at the umbilicus, but becoming less distinct on the lateral area. After bending back again they become once more pronounced, passing across the periphery with a sinus that is concave forwards.

Type
Original Articles
Information
Geological Magazine , Volume 57 , Issue 8 , August 1920 , pp. 351 - 362
Copyright
Copyright © Cambridge University Press 1920

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References

page 352 note 1 Loc. cit., Revision, 1893, p. 54.Google Scholar

page 352 note 2 Loc. cit., 1893, text-fig. 1, p. 5.Google Scholar

page 352 note 3 d'Orbigny's figure (Ter. Jurass., pl. 189, fig. 3) is probably inaccurate.Google Scholar

page 352 note 4 Der Jura am Hermon, Stuttgart, 1887 pl. ii, fig. 3cGoogle Scholar

page 352 note 5 Loc. cit., Revision, 1893, p. 47.Google Scholar

page 352 note 6 Ibid., p. 51.

page 352 note 7 Ibid., p. 52.

page 352 note 8 Loc. cit., Revision, 1893, pp. 40–5.Google Scholar

page 353 note 1 Some of the specimens examined belong to the Astier Collection, preserved in the British Museum (Nat. Hist.), and d'Orbigny stated that, he had received limonitic specimens of A. tortisulcatus from M. Astier (Ter. Crét., p. 164).

page 353 note 2 Loc. cit., 1913, p. 565.Google Scholar

page 353 note 3 Ibid., p. 566.

page 353 note 4 Études de Pal Tunis., i, Ceph. Ter. Second, 1907, p. 16.Google Scholar

page 353 note 5 Loc. cit., 1877, p. 185, pi. xvi, fig. 1–3Google Scholar

page 353 note 6 Loc. cit., 1913, pl. Iiii, fig. 2c.Google Scholar

page 354 note 1 Op. cit., 1910, p. 260, pl. xvi (I), figs. 12–14.Google Scholar

page 354 note 2 Op. cit., 1893, p. 48, pl. i, figs. 4 and 5. This species is not included in the genus Sowerbyceras by Parona & Bonarelli.Google Scholar

page 354 note 3 “Descr. Foss. Ter. Jurass. Mont. Voirons (Savoie)”: Mém. Soc. Pal. Suisse, vol ii, 1875, p. 19, pl. i, fig. 10. In this Argovian form the constrictions are for too deep.Google Scholar

page 354 note 4 Op. cit., 1886, pl. v, fig. 14 only, non pl. iv, figs. 8–10.Google Scholar

page 354 note 5 Op. cit., 1893, pl. i, fig. 12–14.Google Scholar

page 354 note 6 It may be mentioned that Quenstedt (Amm. Schwäb. Jura, p. 762, pl. lxxxvi, and p. 804, pl. xciii) had included in A. tortisulcatus both forms put by Pompeckj into the “ Formenreihe” of Phylloceras ultramontanum, also typical Sowerbycerxs. The writer is not inclined to lay too much stress on the course of the constrictions shown to be variable in many other Phylloceras. On the other hand, Sowerbuceras is probably a descendant of the Bajocian ultramontanus group, as Parona & Bonarelli (loc. cit., p. 117) suggested.Google Scholar

page 354 note 7 Loc. cit., 1870, p. 345.Google Scholar

page 354 note 8 Loc. cit., 1897, p. 142.Google Scholar

page 354 note 9 De, Loriol (loc. cit., 1900, p. 18) was doubtful about the justification of the separation of Ph. subtortisulcatum Pompeekj frum the typical Ph. tortisulcatum d'Orbigny sp.Google Scholar

page 355 note 1 Lethœa geognostica, ii, Mesozoicum, vol. iii, Kreide pt. i Unterkreide, fasc. 2, 1910, p. 171.Google Scholar

page 355 note 2 In Zittel's, Text-book of Palœontology, edited by Eastman, C. R., vol. i, pt. ii, 1900, p. 569.Google Scholar

page 355 note 3 See e.g. Kilian, , Lethœa geognostica, ii, Mesozoicum, vol. iii, Kreide, pt. i, fasc. 2, 1910, p. 174.Google Scholar

page 355 note 4 Ibid., p. 171, and Sayn (“Amm. Pyrit. Marnes Valang, S.E. France”: Mém. Soc. Géol. France, Pal., No. 23, 1901, p. 2) identifies his Valanginian specimens with Zittel's Tithonian ammonites.

page 355 note 5 Loc. cit., 1886, p. 64.Google Scholar

page 355 note 6 Ibid., p. 60.

page 355 note 7 Ibid., p. 64, pl. i, figs. 6, 7.

page 355 note 8 “On certain Genera and Species of Lytoceratidœ”: Q.J.G.S., vol. lxi, 1905 p. 151.Google Scholar

page 355 note 9 Loc. cit., 1898, p. 28 (160), pl. v, fig. 8.Google Scholar

page 356 note 1 In fig. 6c the first lateral saddle is drawn just a shade too slender. On account of the smallness of these specimens collodiotypes could not be taken.Google Scholar

page 356 note 2 Loc. cit., Ter. Jurass., 1842, p. 497.Google Scholar

page 356 note 3 See Pompeckj, , loc. cit., Revision, 1893, text-fig. 24 on p. 115.Google Scholar

page 357 note 1 There were no specimens available for comparison, but the writer was immediately supplied (through the kindness of M. Stuer, of Paris) with three prototypes of Raspail's from Aix (see Haug, loc. cit., 1908, p. 1022)Google Scholar and four specimens from Chaudon, Basses-Alpes (ibid., p. 1023).

page 357 note 2 Loc. cit., 1877, p. 135, pl. xix, fig. 9.Google Scholar

page 357 note 3 Loc. cit., 1892. p. 39, pl. iii, fig. 2a–d.Google Scholar

page 357 note 4 Loc. cit., 1872, p. 14, pl. iv, figs. 2, 3.Google Scholar

page 357 note 5 Favre, , “Descr. Foss. Terr. Oxf. Alp. Frib.”: Mém. Soc. Pal. Suisse, vol. iii, 1876, p. 35.Google Scholar

page 357 note 6 According to Gemmellaro's description, not the figures cited. Pl. iii, fig 3, in Favre (loc. cit.) is very near, being the young.Google Scholar

page 357 note 7 Haug, , loc. cit., 1908, pp. 1019–53.Google Scholar

page 357 note 8 Loc. cit., 1897, p. 109.Google Scholar

page 357 note 9 Ibid., p. 143.

page 358 note 1 Montagne, de. Lure, Paris (Masson), 1889, p. 79.Google Scholar

page 358 note 2 A. polystoma Quenstedt is recorded from a “black limestone of macrocephalus age” from Barrème.Google Scholar

page 358 note 3 This author (Traité de Pal., vol. ii, 1854, p. 698) stated that A. tripartitus was characteristic of the Callovian in France, and was found in Germany, together with A. Murchisonœ.Google Scholar

page 358 note 4 In Geologie d. Schweiz, 1853, vol ii, p. 45, A. tripartitus is recorded as occurring, with Phylloceras zignodianum and Macrocephalites, in the Callovian, but on p. 52 it is associated with S. tortisulcatum, Ph. tatricum, and also A. plicatilis, and put into the Oxfordian.Google Scholar

page 358 note 5 “Jurass. Chaîne Nerthe et l'Étoile”: Bull. Soc. Géol. France, ser. III, vol. xxvi, 1898, p. 520. Ph. mediterraneum and Oppelia here occur with P. tripartitus.Google Scholar

page 358 note 6 Loc. cit., 1886, pl. ix, fig. 13Google Scholar. Buckman, S. (“Certain Jurassic Species of Amm. and Brach.”: Q.J.G.S., vol. lxvi, 1910, p. 96) is inclined to put this as low as the discites zone.Google Scholar

page 358 note 7 Loc. cit., 1897, p. 129, pl. iii, fig. 1.Google Scholar

page 358 note 8 Loc. cit., Ter. Jurass., p. 421, pl. 146Google Scholar, and Favre, , “Contrib. à l'Etude des Oppelia”: Mem. Soe. Pal. Suisse, vol. xxxviii, 1912, p. 31.Google Scholar

page 359 note 1 Tsytovitch (“Le genre Heeticoceras”: Mém. Soc. Pal. Suisse, vol. xxxvii, 1911) has again drawn attention to the difficulty of separating Hecticoceras and Lunuloceras on purely morphological grounds.Google Scholar

page 359 note 2 Der Jura am Hermon, 1887, p. 18, text-fig. 3.Google Scholar

page 359 note 3 Loc. cit., 1912, fig. 1 on p. 13.Google Scholar

page 360 note 1 As represented by e.g. “Oppelia” retrocoslata Grossouvre (“Etudes sur l'Etage Bathonien ”: Bull. Soc. Geol. France, ser. m, vol. xvi, 1888, p. 374, pl. iii, figs. 8, 9), and the Cornbrash species “ Harpocerans” (Ludwigia) «subpunctatum (Schlippe “ Fauna Bath. Oberrhein. Tiefl.”: Abh. Ceol. Spec. K. Els.-Lothr. vol. iv, 1888, No. 4, p. 196, pl. v, fig. 3). Haug (loc. cit., 1898, p. 82) considers them identical.Google Scholar

page 360 note 2 Amm. Schwäb. Jura, 1887, pl. lxxxii, e.g. figs. 23 and 32.Google Scholar

page 360 note 3 Loc. cit., 1873, e.g. pl. xiii.Google Scholar

page 360 note 4 Loc. cit., 1910, e.g., pl. xviii (iii).Google Scholar

page 360 note 5 Loc. cit., 1898, e.g. H. Bonarellii, de Loriol, pl. iii, figs. 19–21, and 1900, pl. iii, p. 14.Google Scholar

page 360 note 6 Loc. cit., e.g. “Harpoceras” Guthei, Noetling, p. 20, pl. ii, figs. 6–8a.Google Scholar

page 360 note 7 Loc. cit., 1852, pl. ii, figs. 9–13.Google Scholar

page 360 note 8 Loc. cit., 1905, text-fig. 9 on p. 19.Google Scholar

page 361 note 1 Till, , op. cit., 1910, i, p. 185.Google Scholar

page 361 note 2 Also recorded by Suess (Das Antlitz der Erde) from Zanzibar.