THE LIAS AMMONITES. 



The Zone of Avictjla contorta. 

 '. — Von Bucli, " Scliicht mit Gervillien auf der Gruber Alp am Setzberge 

 in den bayr. Alpen," Denksch. Akad. Wissensch. Berlin, Jahrg. p, 82, 1828. Alberti, 

 " Versteinerungsreicher Sandstein von Tabingen," 1834. Strickland, " Calcareous Sand- 

 stone with Pectens, and White Micaceous Sandstone with Bivalve Shells." Proceedings 

 of the Geological Society, vol. iii, p. 586, 1842. Portlock, " Shale " with Avicula 

 contorta and " loose gritty marl " containing Pecten Valoniensis, Report on Geology of 

 Londonderry, pp. 126, 127, 1843. Brodie, " Pecten-bed," Fossil Insects of the Secon- 

 dary Rocks, p. 58, 1845. Quenstedt, " Gelbe Sandsteine," Elozgebirge Wiirttem- 

 bergs, 1846. Emmerich, " Gervillien-Schichten," Neues Jahrbuch, p. 437, 1849. 

 Schafhautl, " Schiefergebilde der Wetzsteinformation mit Gervillien," Geognost. 

 Untersuch. siidbayrischen Alpengebirges, 1851. Von Hauer, " Kossener-Schichten," 

 Jahrbuch der k. k. geologischen Reichsanstalt, p. 733, 1863. Escher, " Oberes St.- 

 Cassian.," Geologische Bemerkungen iiber Voralberg, 1853. Giimbel, Gervillien- 

 (K6ssener-)Schichten in der Grllnten," Geognostische Skizze, 1856. Oppel and Suess, 

 "Kossener-Schichten," Sitzungsber. Akadem. Wissenschaft. Wien, vol. xxi, p. 525, 

 1856. Oppel, " Kossener-Schichten," Jura, p. 290, 1856. Winkler, " Die Schichten der 

 Avicula contorta inner- und ausserhalb der Alpen," 1859. Oppel, " Die Zone der Avicula 

 contorta," Wurttemberg. natur. Jahreshefte, p. 315, 1859. Lyell, " Infra-hassic Strata 

 of Austrian Alps," Supplement to the Manual of Geology, 5th ed., 1857. Suess, " Koss- 

 ener-Schichten," Leber die Brachiopoden, &c., 1854. Jules Martin, "Infra-Lias" 

 (pars), Paleontologie stratigraphique de I'lnfra-Lias du Departement de la Cote-d'Or, 

 Mem. Soc. Geol. Erance, 2 serie, vol. vii, 1860. Stoppani, Essai sur les condi- 

 tions generales des couches a Avicula contorta, 1861, supplement a I'essai 1863. 

 Alphons V. Dittmar, Die Contorta-Zone ihre Verbreitung und ihre organischen 

 Einschliisse, 1864. Renevier, Notices geologiques et paleontologiques sur les Alpes 

 Vaudoises, p. 1, 1864. Dumortier, " Infra-Lias, zone a Avicula contorta" Etudes Paleont. 

 sur les Depots Jurass. du Bassin du Rhone, torn, i, p. 6, 1864. Boyd Dawkins, 

 " Rhaetic Beds," Journ. Geol. Soc, vol. xx, p. 396, 1864. Das Rhat in der Umgegend v. 

 Gottingen, L. Pfliicker y Rico, Berlin, 1868. Brauns, Die untere Grenze des Jura und 

 die ihr zunachst liegenden Triasschichten, p. 22, 1871. Tate and Blake, Yorkshire Lias, 

 " The Rhsetic Series and the relations of the Lias with the Keuper," p. 30, 1876. 



The Avicula contorta beds, as proved by the above list of synonyms, have for forty 

 years engaged the attention of geologists, who, after much discussion as to their 

 true place in the series, are still divided in opinion as to whether they ought to be 

 considered the upper portion of the Keuper or the basement-beds of the Lias. It is 

 now generally admitted that the fades of the fauna of the Avicula contorta zone has 

 more affinities with the Kossener-Schichten of the Tyrol and the Upper St.-Cassian beds 

 of Germany than with the true Lias, and it can be demonstrated that most of the 

 species of Badiata, Mollusca, and Fishes, found in the Avicula contorta beds, are special 

 to them, and do not pass into the Lias. 



