452 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Apr. 18, 



the Lias, which is well developed, the beds of the Dachstein Lime- 

 stone, characterized by numerous Corals and a large bivalve {Mega- 

 lodon scutatus of SchafhJiutl, " Dachstein bivalve" of the Austrians). 

 Below the Dachstein limestone are the Gervillia-beds (lately called 

 Kossen-beds by Von Hauer). The Cardita crenata, Goldf., the Avi- 

 cidce of the famil}^ of the GryphceatcB, and small turrited univalves, 

 contained in these beds, induced me to refer them to some of the 

 St. Cassian beds. Lower still are thickly developed masses of dolo- 

 mite, under which sandstones with impressions of Keuper plants 

 occur. 



The exact relation of the Salzburg beds containing Ammonites 

 globosus with the Gervillia-beds has not yet been made out. We 

 have not hitherto been able to find in the Alps of the Vorarlberg this 

 characteristic family of Ammonites. 



In the vicinity of the Lake of Como, the dolomitic masses change 

 their appearance ; but beneath the lias the Gervillia-beds form a good 

 geological horizon, which can be found in numerous places when 

 once one has become accustomed to its position. This bed is also 

 found under the Lias of the chain of the Stockhorn, Canton Berne ; 

 and Escher has found it in the neighbourhood of Geneva. 



We have called the whole of the beds situated between the Lias 

 and the Keuper, " St. Casciano formation.'" It is a marine formation, 

 which appears to be wanting in the North of Europe, and which is 

 only developed in the South, commencing with the chain of the Alps, 

 and in Eastern Europe. In a palseontological point of view, it is 

 distinguished from the overlying Lias by the absence of Belemnites, 

 and from the Trias, on which it lies, by the existence of Ammonites 

 with foliated septa. 



You know that the Austrian geologists formerly considered the 

 *' Dachstein Limestone " as Lower Muschelkalk. Von Buch and 

 his successors thought that the Gervillia-beds should be placed on a 

 parallel with the Brown Jura. It is easy to perceive how such sup- 

 positions must have obscured the geology of the Western Alps ; but 

 this has become much clearer since the true position of the different 

 beds has been better established. 



The Austrian geologists are now of the same opinion as ourselves 

 respecting the true position . of the Dachstein Limestone and of the 

 Gervillia-beds (their Kossen-beds). They connect them nevertheless 

 with the Lower Lias, and they consider the beds with Ammonites glo- 

 bosus at Salzburg, and those of St. Cassian, as a separate formation, 

 which they call Upper Muschelkalk. This is a questionable point, 

 which will be decided, I hope, as soon as we get more positive data 

 respecting the position of the Ammonites globosus of Salzburg, a time 

 which is not far distant. 



It appears that the true Muschelkalk is wanting along the whole 

 northern slope of the Western Alps ; it reappears to the south. Be- 

 sides the localities already known, Escher has discovered several 

 others. I have lately received from Messrs. Lavizzaci and Stabile at 

 Lugano a considerable number of fossils found in the well-known 

 dolomite of the chain of Monte Salvadore, near Lugano, which most 



