THE 



GEOLOGICAL MAGAZINE 



NEW SERIES. DECADE VI. VOL. II. 



No. III.— MARCH, 1915. 



ozr.ig-hst.a.iij ARTICLES. 



In^h 





I. — On Schlotheimia Gheenoughi, J. Sowkrby, sp. 



By L. F. Spath, B.Sc, F.G.S. 



(PLATE IV.) 



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 

 Gr.eenoughi, 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, 1 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 2 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. 



It will be shown in the following pages that whereas Amaltheus 

 Greenoughi (Sowerby), Wright, had, by most recent writers, been 

 regarded as an Oxynoticeras z from the oxynotum zone, Sowerby's form 

 is a Schlotheimia, and appears to be restricted to the Bucklandi beds, 

 or, more correctly, to the rotiforme subzone 4 only. The matter seemed 

 of sufficient importance to be recorded without delay. 



There are now in the Sowerby Collection in the British Museum 

 two specimens bearing the original Sowerby label, "Ammonites 



1 F. A. v. Quenstedt, Die Atnmoniten des Schioab. Jura, vol. i, p. 297, 1885. 



2 J. F. Pompeckj, " Notes sur les Oxynoticeras, etc. " : Comm. Serv. Geol. 

 Port., vol. vi, fasc. 2, p. 264, 1906. 



3 Neumayr in 1875 ("Die Ammon. der Kreide, etc.": Zeitsehr. Deutsch. 

 Geol. Ges., vol. xxvii, p. 886) first ..put A. Greenoughi, Sow. (Hauer) into the 

 genus Amaltheus, and in 1878 ("Uber unvermittelt auftretende Cephalop." : 

 Jahrb. k. k. Beichsanst., vol. xxviii, p. 61) 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. 296) referred the form to the genus" Phylloceras ; and in H. B. 

 Woodward (Jurassic Rocks of Britain, vol. iii, p. 336) both Amaltheus and 

 Phylloceras are given. S. S. Buckman (in L. Bichardson, Geology of 

 Cheltenham, 1904, p. 212), on the other hand, assigned the form to the genus 

 Agassiceras \_Agassizoceras\. 



4 i.e. Lower Bucklandi zone ; see S. S. Buckman, Yorkshire Type 

 Ammonites, vol. i, p. xvi, 1910. 



DECADE VI. — VOL. II. — NO. III. 7 



