LYTOCERAS HIRCINUM. 



415 



Lytoceras HIRCINUM, SMotheim. PI. LXXV, figs. 4—7 ; PI. LXXVI, fig. 6. 



Ammonites Knorr. Sammlung von Merkwiirdigkeiten, pt. ii, 



pi. i, figs. 1,2; pi. A, fig. 12, 1750. 

 Ammonites niuciNUS, Schlotheitn. Petrefaktenkunde, No. 19, p. 72, 1820. 



— — Be JJaan. Ammonit. et Goniatit., p. 130, 1825. 



— INTERRUPTUS, Zieteti. Verstein. Wiirtemb., tab. XV, fig. 3, 1830. 



— OBLIQUE INTERRUPTUS, Schiibler in Zieten. Ibid., tab. xv, fig. 4, 1830. 

 cTOrbigny. Pal. Fran9., Ter. Jiirass., p. 320, 



pi. 101, 1842. 

 Quenstedt. Flbzgebirge Wiirtemb., p. 273, 1843. 

 — Cephalopoden, p. 103, tab. vi, figs. 



10 a, 6, c, 1849. 

 Giebel. Fauna der Vorwelt, Bd.iii, p. 402, 1852. 

 Oppel. Jura Formation, p. 254, 1856. 

 Lycett. Cotteswold Hills Handbook, p. 123, 



pi. ii, fig. 7, 1857. 

 Quenstedt. Der Jura, p. 280, tab. 40, figs. 3—8, 



1858. 

 Brauns. Der Mittlere Jura, p. 103, 1869. 

 Dumortier. Depots Jurassiques, torn, iv, p. 117, 



1874. 

 Neumayr. Zeitschr. Deutsch. geol. Geselisch., Bd. 



xsvii, p 893, 1875. 

 Tate and Blake. Yorkshire Lias, p. 298, 1876. 



— Germanii, 



HIRCINUS, 



— Leckenbyi, 



— HIRCINUS, 



LyTOCEEAS HIRCINUM, 



— Germanii, 



Diagnosis. — Shell discoidal, compressed, not carinated ; whorls one-third involute, 

 flattened on the sides, narrowing and rounded at the siphonal area; shell with small, 

 annular, oblique ribs, interruptedly sulcated with twelve to fourteen marked constrictions, 

 which are deepest on the siphonal area ; umbilicus widely open ; aperture oval. 



Dimensions. — Transverse diameter 60 millimetres; width of umbilicus 18 miUi- 

 metres ; height of aperture 25 millimetres. 



Description. — This Ammonite is nearly always found in England as a mould (PI. 

 LXXV, figs. 4 — 7) and seldom has any shell preserved. The mould is discoidal, com- 

 pressed, the sides convex and flattened, the siphonal area narrow and extremely convex, but 

 not carinated. When the shell, which is extremely thin, is preserved (PI. LXXVI, fig. 6) 

 it is ornamented with numerous delicate oblique striations or fine costae ; and on the 

 last whorl there are about twelve to fourteen oblique sulcations, which were occupied by 

 prominent ribs that extended beyond the intermediate costse. The sulci are deeper and 

 more marked on the siphonal area ; and, as they approach the aperture, the constrictions 

 are very deep in the two outer whorls ; but are absent in the inner ones, and they 

 likewise disappear in the old shells. The spire is formed of six very narrow cylindrical 



