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I.—On Schlotheimia Greenoughi, J. Sowerby, sp.

Published online by Cambridge University Press:  01 May 2009

L. F. Spath
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Extract

While working at the Lower Liassic Ammonites of the Sowerby Collection, preserved in the British Museum (Nat. Hist.), the author happened to come upon one of the paratypes of Ammonites Greenoughi, J. Sowerby, which could be recognized at once as being allied to Schlotheimia Charmassei, d'Orbigny, sp. On going into the matter in greater detail it was found that the suspicions of some Ammonite workers regarding the misinterpretation of the species by most previous authors were, indeed, well founded. Quenstedt, for example, had stated that Wright, having found Sowerby's type very much disfigured by decomposition of pyrites, substituted for it a gigantic specimen of a diameter of 440 mm., “which, however, looks different again.” Pompeckj again stated that the gigantic specimen drawn by Wright, as well as his description defined the species in a not very precise manner, and that, therefore, it was not certain that the specimen agreed with Sowerby's original.

Type
Original Articles
Information
Geological Magazine , Volume 2 , Issue 3 , March 1915 , pp. 97 - 102
Copyright
Copyright © Cambridge University Press 1915

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References

page 97 note 1 Quenstedt, F. A. v., Die Ammoniten des Schwäb. Jura, vol. i, p. 297, 1885Google Scholar.

page 97 note 2 Pompeckj, J. F., “Notes sur les Oxynoticeras, etc.”: Comm. Serv. Geol. Port., vol. vi, fasc. 2, p. 264, 1906Google Scholar.

page 97 note 3 Neumayr in 1875 (“Die Ammon. der Kreide, etc.”: Zeitschr. Deutsch. Geol. Ges., vol. xxvii, p. 886Google Scholar) first put A. Greenoughi, Sow. (Hauer) into the genus Amaltheus, and in 1878 (“Über unvermittelt auftretende Cephalop.”: Jahrb. k. k. Reichsanst., vol. xxviii, p. 61Google Scholar) he included it in the group Fissilobati of that genus, together with a heterogeneous mixture of other Ammonites. Wright, in 1882, followed Neumayr, but Tate & Blake (in Yorkshire Lias, 1876, p. 296Google Scholar) referred the form to the genus Phylloceras; and in Woodward, H. B. (Jurassic Rocks of Britain, vol. iii, p. 336)Google Scholar both Amaltheus and Phylloceras are given. Buckman, S. S. (in Richardson, L., Geology of Cheltenham, 1904, p. 212)Google Scholar, on the other hand, assigned the form to the genus Agassiceras [Agassizoceras].

page 97 note 4 i.e. Lower Bucklandi zone; see Buckman, S. S., Yorkshire Type Ammonites, vol. i, p. xvi, 1910Google Scholar.

page 98 note 1 Wright, T., Lias Ammonites (Mon. Pal. Soc.), 1882, p. 384Google Scholar.

page 98 note 2 Mineral Conchology, vol. ii, p. 71, pl. 132, 1816Google Scholar.

page 98 note 3 This distance, in the large, comparable specimens, amounts to about one whole whorl, and it is probable, therefore, that Sowerby’s figure is reduced to, perhaps, as much as one-third of the original diameter, especially since he states that specimens vary in size from 12 to 18 inches in diameter. The suture-line itself has the lateral saddle higher and larger than the external saddle, and is apparently of a Schlotheimia pattern. Only the last ones at about 200 mm. diameter are visible (at a in the figure), but they are, unfortunately, not clearly traceable.

page 98 note 4 T. Wright, op. cit., pl. xliv.

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page 100 note 10 Hug, O., “Beitr. Kenntn. Lias & Dogger Amm. Freiburger Alpen,” II: Abh. Soc. Pal. Suisse, vol., xxvi, p. 6, 1899Google Scholar.

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page 101 note 6 Böse, E., however, had pointed out in 1894 (“Fleckenmergel”: Zeitschr. Deutsch. Geol. Ges., vol. xlvi, p. 747)Google Scholar that A. guibalianus, d’Orbigny, sp., and A. Greenoughi, J. Sowerby, could not be united as they were by Hyatt, since the ribbing was quite different “if one could judge at all from the bad original figure”. We have seen already that Sowerby’s figure was for his time very good, but authors, unfortunately, do not seem to have consulted the text. On p. 70 Sowerby also made the important remark (which apparently had quite scaped attention) that A. Conybeari and A. Greenoughi were generally companions in the same stratum, and were occasionally impressed with each other’s type.

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