284 THE LIAS AMMONITES. 



which is quite the reverse in A. Crossii. The amount of involution is likewise much less 

 in A. BucMandi, and the keel is thicker and more pronounced in that form than in 

 A. Crossii. 



Locality and StratigrapMcal Position. — This interesting Ammonite was found in the 

 Scunthorpe Ironstone, associated, according to the Rev. J. E. Cross, with A. BucMandi, 

 A. Conybeari, A. semicostatus, A. stellaris, Aegoceras Boucaultianum, Nautilus striatus, 

 Belemnites acutus, Pleurotomaria Anglica, Cardinia gigantea, and Lima antiquata, 

 which are considered to represent the Upper BucMandi-series, or zone with A. semicostatus. 

 See p. 41. 



I know of no other British specimens except those belonging to Mr. Cross's Collec- 

 tion. In the Museum of Stuttgart, however, I observed two very fine specimens of this 

 species in the upright cases, unnamed, as they had been separated by Prof. Fraas from the 

 true BucMandi forms, and placed there as distinct. In the Museum of Tubingen, Professor 

 Quenstedt kindly showed me another large specimen, and informed me that it came 

 from the Upper BucMandi-bed at Gmiind and Goppingen. My learned friend, who is 

 most particular about the position of all fossils, assured me that it was the true horizon 

 of this species, which I have named in honour of the Rev. J. E. Cross, F.G.S., its 

 discoverer in the British Lias. 



Arietites semicostatus, Young and Bird. PI. I, figs. 4 — 8. 



Ammonites semi-costatus, Young fyBird. Geol. Surv. York. Coast., pi. xii, fig. 10, 



p. 257, 1828. (2nd. Edit.) 



— kkidion, Hehl? Zieten's Verstein. Wiirttemb., p. 4, pi. iii, fig. 2, 



1830. 



— natrix, Roemer. Oolithen-Gebirg. i, p. 193, 1836. 



— kridion, d'Orbigny. Pal. Francaise, Terr. Jurass., pi. li, figs. 1 — 6, 



p. 205, 1842. 



— semi-costatus, Simpson. Monogr. of the Ammonites, p. 51, 1842. 



— Bodleyi, Buckman. Murchison's Geol. of Cheltenham, 2nd ed., 



p. 43, as crenata, pi. xi, fig. 7, 1845. 



— geometricus, Oppel. Juraformation, p. 79, 1856. 



— nodosaries, Wagener. Verh. Nat. Ver., p. 161, 1860. 



— spinaries, Wagener. Ibid., 1860. 



— geometricus, Schloenbach. Neues Jahrb., 1863, p. 164 ; Zeitsch. d. d. 



Geol. Gesellschaft, vol. xv, p. 500, 1863. 

 _ — Schloenbach. Beitriige zur Palaontol., Palaeontographica, 



vol. xiii, p. 155, pi. xxvi, fig. 3, 1865. 



— falcaries, Quenstedt. Der Jura, p. 70, tab. vii, figs. 6, 7, 1858. 



— semi-costatus, Simpson. Fossils of the Yorkshire Lias, p. 93, 1855. 



