346 



TPIE LIAS AMMONITES. 



Aegoceras Davcei, Sowerhy. PI. XXXI, figs. 1, 2. 



Ammonites Davcei, Sowerly. Min. Conch., vol. iv, p. 71, pi. 350, 1822. 

 Planites — de Haan. Ammonit. et Goniatit., p. 82, No. 3, 1825. 

 Ammonites — Zieten. Versteiner. Wurttembergs, p. 19, tab. xiv, fig. 2, 1830. 



— — Roemer. Norddeutschen Oolithgebirg., p. 199, 1836. 



— Datoei, Bronn. Lethsea geognost., p. 447, tab. xxiii, fig. 4, 1837. 



— — CoUegno. Bulletin Soc. ge'olog. de France, x, p. 247, 1839. 



— — Quenstedt. Flozgebirge Wiirtembergs, 171, 1843. 



— Dav^i, d'Orbigny. Pal. Fran9. Juras., torn, i, p. 276, pi. 81, 1842. 



— — Quenstedt. Cephalopoden, p. 91, tab. 5, figs. 6, 1849. 



— — Savi and Meneghini. Consid. Geologia Toscana, p. 115, 1851. 



— — Studer. Geologie der Schweiz, t. ii, p. 31 — 35,1853. 



— — Meneghini. Nuovi Fossili Toscani, pp. 10, 31, 1853. 



— Davoi, Oppel. Mittlere Lias Schwabens, Jahreshefte Wiirttemberg, p. 80, 



1853. 



— — Quenstedt. Der Jura, p. 132, 1858. 



— — Von B.auer, Die Cephalopoden aus dem Lias der Nord-Ost. 



Alpen, p. 54, pi. xvii, figs. 11, 12, 1856. 



— — Chapuis. Terr. Sec. de Luxenib., p. 25, t. iv, fig. 5, t. v, fig. 1, 



1858. 



— — Dumortier. Depots Jurassiques du Bassin du Rhone, torn, iii, 



p. 94, pi. xi, figs. 4—6, 1869. 

 Aegoceras Davoei, Neumayr. Zeitschrift der Deutsch. geol. Gesellschaft, p. 906, 

 1875. 



Biagnosis. — Shell discoidal, depressed ; umbilicus wide ; whorls round, slightly 

 involute, covered on the sides and area with numerous simple, narrow, oblique ribs ; on 

 each revolution of the spire there are eight to ten round, obtuse 

 tubercles developed near the middle of the whorl, and occu- 

 pying the width of three ribs ; siphonal area rounded, slightly 

 depressed, and covered with numerous transverse close-set 

 costae; spire formed of eight whorls, which are round and 

 slightly depressed on the outer margin ; aperture roundish. 



Dimensions. — The large figured specimen ; transverse dia- 

 meter 112 millimetres; wddth of umbilicus under aperture 65 

 miUimetres ; vertical height of whorl 26 millimetres ; transverse 

 diameter 30 millimetres. The specimens found in general are 

 much smaller, two before me measure transverse diameter 90 

 millimetres ; width of umbilicus under aperture 55 millimetres ; vertical height of last 

 whorl 22 millimetres ; transverse diameters 23 millimetres. 



Description. — This beautiful Ammonite is a very rare British fossil. The specimen 



Fig. 188. — Aegoceras Bavoei, 

 Sow. 



