STRATIGRAPIIICAL GEOLOGY. 479 



their work of surveying, palaeontologists found matter for 

 discussion in the faunal affinities of the Avicula contorta zone 

 whether the fossils indicated nearer relationship to the 

 Keuper fossils below or to the Liassic fossils above them. 



Alberti and Plieninger, the two leading Swabian authorities, 

 thought them distinctly Triassic in character, and included the 

 Avicula contorta zone or Bone-bed as the uppermost member 

 of the Keuper; Quenstedt, after some hesitation, distinguished 

 the fauna as an intermediate assemblage occurring in passage- 

 beds and premonitory of the Lias. Oppel (1856), Sedgwick, 

 Murchison, and the great majority of the Austrian geologists 

 at that time assigned the Avicula contorta zone to the Lias ; 

 Emmrich, Merian, Studer, and Escher von der Linth placed it 

 in Upper Trias. In France, geologists had long been familiar 

 with the fossiliferous deposits between Keuper and Lias, as 

 these are well'exposed over a considerable tract of country on 

 the east and south of the Central Plateau and in Lothringen. 

 Leymerie had described them in 1840 under the name of 

 fnfra/tas, but many of the later authors grouped them with 

 Trias. The same difference of opinion reigned in Great Britain; 

 Brodie and Strickland (1842) regarded the passage series with 

 the bone-bed as Liassic, whereas Agassiz (1844) and Buckmann, 

 on the basis of the Fish and Plant remains, declared the series 

 to be Triassic in character. 



Oppel and Suess gave in their first memoir no expression of 

 opinion regarding the Triassic or Liassic age of the beds ; the 

 relative stratigraphical position sufficed for their immediate 

 purpose. But in 1859 Oppel contributed a special memoir, 

 and stated that after tracing the extra-Alpine " Contorta-zone " 

 into Luxembourg and France, he had come to the conclusion 

 that the limiting-line between Trias and Jura should be above 

 the "Contorta" strata and below the zone of Ammonites 

 planorbis. Two years later this view was supported by 

 Giimbel in his Geognostic Description of the Bavarian 

 Alps (1861). Giimbel proposed to group the Kossen strata 

 and the Dachstein limestone together under the name of 

 Jkhcetic Group, from their development in the Rhaetikon 

 district of the Alps, and to regard this group as the upper- 

 most division of the Alpine Keuper. At the present day 

 most of the German and Austrian geologists follow Giimbel's 

 suggestion ; but in France the majority of the geologists retain 

 the position and the name " Infralias," which was suggested by 



