380 THE LIAS AMMONITES. 



mould, whilst the ribs and tubercles on the sides and siphonal area are distinctly visible 

 throughout. 



Affinities and Differences. — The outer whorl of Aec/. striatum resembles the body 

 chamber of Aeg. Henleyi^ but the inner whorls are quite distinct in form and structure 

 in the two shells. The umbilicus is deep and narrow in Aeg. striatum and wide and 

 open in Aeg. Henleyi^ and the arc of the circle described by Aeg. striatum is that of a 

 much smaller circle than the one which is represented by Aeg. Ilenleyi. The one 

 Ammonite {Aeg. Ilenleyi) undergoes an important change of form about the sixth whorl 

 of its age the other {Aeg. striatum) appears to retain its form and characters without 

 much change through life. 



Locality and StratigrapJiical Position. — This appears to be a very abundant and 

 leading Ammonite of the Middle Lias, with an extensive distribution in time and space. 

 It is found in the Ilenleyi zone at Eenny Compton, Warwickshire ; Radstock, Somerset- 

 shire ; Lyme Regis, Dorsetshire ; and Robin Hood's Bay, Yorkshire. In Gloucestershire 

 it is found in the Aeg. Ilenleyi zone of the Cotteswolds Hills at Hewletts, near Chelten- 

 ham, Whitcombe, near Gloucester, and in other exposures of these beds. 



Foreign Distribution. — In Erance the late Professor d'Orbigny noted this species at 

 Saint Amand, Cher; Eontaine-Etoupe-Eour, Croisilles, Curcy, Landes, Calvados; Breux, 

 Meuse ; Mulhausen, Bas Rhin ; Pouilly, Semur, Venarey, Cote-d'Or ; Avallon, Yonne ; 

 the late Mons. Dumortier cites Saint-Fortunat, Saint-Cyr, Saint-Diedier, Rhone ; he 

 collected a magnificent example, 190 millimetres in diameter, in a region where Jurassique 

 fossils are little known, in the middle of Erance, at the foot of the Pyrenees, at Albas, 

 Aude. In Germany the typical example figured by Reinecke was discovered in Coburg. 

 In Swabia it is found pyritic, associated with Amaltheus ibex in the middle region of 

 Amaltheus margaritatus^ but it is not obtained from either higher or lower zones. 



Aegoceras Bechei, Sowerby, PL XLI, figs. 1 — 5. 



Ammonites Bechei, Soiverhy. Mineral Cotichology, vol. iii, p. 143, pi. 280, 1821. 



— — Zeiten. VersteinerungenWiirttembergs, p. 37, tab. xxviii, fig. 4, 



1830. 



— — cVOrhigmj. Pal6ontol. Franqaise Terr. Jurass, t. i, p. 2"8, pi. 



Ixxxii, 1842. 

 _ _ Quenstedt. Cephalopoden, p. 135, 1849. 



— — Ton Strumheck. Obere Lias, Zeitschr. Deutsch. geol. Gess., v, p. 



82, 1853. 



— — Simpson. Fossils of the Yorkshire Lias, p. 70, 1855. 



Diagnosis. — Shell globose, last whorl much inflated, highly involute, and entirely 

 covered with fine longitudinal striations ; sides ornamented with two rows of small 



