AMALTHEUS OXYNOTUS. 387 



The aperture has an elhptico-lanceolate figure, and is deeply occupied by the 

 penultimate whorl. 



The lobe-line is very complicated, and drawn with difficulty. Fig. 5 is from a tracing 

 made upon a mould, which shows the lines most distinctly ; it differs somewhat from the 

 figure given by d'Orbigny. The siphonal lobe, longer and much larger than the 

 principal lateral lobe, is formed of a large terminal branch and three other branches 

 on each side. The siphonal saddle, much wider than the principal lateral lobe, terminates 

 in five-lobed folioles. The principal lateral lobe has a central stem with two lateral 

 divisions on each side and two terminal branches. The lateral saddle is one third 

 wider than the principal lateral lobe, and terminates in five- or six-lobed folioles. The 

 lateral lobe, much smaller than the principal, has an oblique stem with small lateral 

 branches on each side, and a terminal twig with trifid digits. 



The auxiliary saddles, three in number, diminish in size from without inwards, and 

 the three auxiliary lobes are short with many points on their margins. 



The septa are closely approximated in the shell, and when the lobe-lines are seen in 

 situ on the sides, they exhibit a most complicated labyrinth of lines very difficult to trace 

 out on the mould. 



Affinities a7id Differences. — This Ammonite occupies, as d'Orbigny remarked, an inter- 

 mediate position between Amal. margaritatus and Amal. cordatus (fig. 190). It is distin- 

 guished from both by its more prominent and better defined carina, and the absence of 

 the cordlike structure of the one shell and the serrated structure of the other. Its whorls 

 likewise are much more involute, and its lobe-line very difierent from both. 



Locality and Stratigraphical Position. — I have found this Ammonite near Cheltenham, 

 and possess a good .series of well-preserved examples from the Amal. oxt/notus-hed of the 

 Lower Lias. I know no Ammonite which maintains, so constantly and with so little 

 change, its specific form through all its morphological history as does this species. 



Amalthetjs OXYNOTUS, Quenstedf. PI. XLVI, figs. 4 — 6. 



Ammonites maeandeus ?, Zieten. Die Versteinerung. Wiirltembergs, p. 12, tab. ix, 



fig. 6, 1830. 



— oxYNOTCS, Quenstedt. Flozgebirge Wiirtetnbergs, p. 161, 1843. 



— POLYOPHYLLUS, Simpson. Monograph of the Ammonites of Yorkshire 



Lias, p. 39, 1843. 



— RoBiNsoNi, — Ibid., p. 42, 1843. 



— BucKii, — Ibid., p. 42, 1843. 



— OXYNOTUS, Quenstedt. V. Leonhard and Bronn'sJahrbuch, p. 87, 1845. 



— cuLTELLUS, Buchman. Geology of Cheltenham, p. 103, tab. xii, 



figs. 4, 5, 1845. 



— OXYNOTUS, Quenstedt. Petrefactenkunde Cephalopod., pp. 98, 262, 



tab. V, fig. 11, 1849. 



