STRATIGRAPHICAL GEOLOGY. 505 



and those of similar age in England and France - } at the same 

 time Buch expressly stated that in consideration of the many 

 contrasts presented by the South German facies, both palaeonto- 

 logically and lithologically, it is very undesirable to attempt to 

 apply the English nomenclature. It was shown that the three 

 leading gioups might be again sub-divided into a number 

 of palaeontological zones characterised by certain definite 

 leading fossil types ("Leitmuscheln "). Buch concluded this 

 interesting work by an enumeration of one hundred and two 

 carefully described species of the " leading molluscan types " 

 characteristic of the successive rock-horizons. 



The foundation was thus laid for the geology of the Swabian 

 and Franconian Jura by Buch, but the main structure was 

 built up by F. A. Quenstedt in after-years in his memorable 

 treatise Das Flotzgebirge Wilrtembergs (1843 an d 1851). The 

 three chief divisions of Buch are sub-divided into sub-groups 

 and zones according to their petrographi'cal development 

 and palaeontological features, and the zones are distinguished 

 by letters of the Greek alphabet. In this way the Lias 

 and the brown and white Jura are each of them resolved 

 into six zones, the oldest of which is designated as a, the 

 youngest as Quenstedt's eighteen zones of the Wiirtem- 

 berg development of the Jurassic system have since shown 

 themselves to be well founded, although they are not all of 

 equal palaeontological value. Clearly Quenstedt, for the sake 

 of symmetry in the number of zones, defined some of them 

 within rather narrower limits than others. 



It was a great deficiency in Quenstedt's work that he had 

 made no attempt to describe the tectonic structure of the 

 area, or even to show by maps or sections the stratigraphical 

 mode of occurrence of the strata. In 1853, Quenstedt remedied 

 this by publishing a typical geological section of the Swabian 

 Jura carried out by his pupil W. Pfizenmayer (Zeitsch. d. d. geoL 

 Ges., Taf. xvi.). 



The work, however, which gave Quenstedt a pre-eminent 

 place in the roll of fame was that which appeared in 1858 

 under, the simple title of Der Jura. In it Quenstedt gave a 

 marvellously attractive exposition of the results of his nineteen 

 years' researches on this formation ; the description and 

 illustrations of the fossils in Der Jura are excellent, and the 

 keen and accurate observation even of the most concealed 

 features calls forth the highest admiration. The work found 



