1848.] 



MURCHISON ON THE STRUCTURE OF THE ALPS. 



193 



S.S.E. 



In following our formation into the valley which extends from Brun- 

 nen to Schwyz, on the eastern shores of the lake of Lucerne, we found 

 that the intermediate succession between the neocomian and the 

 flysch became much more regular and distinct. Situated between 

 the Rigi (that grand accumulation of nagelflue and molasse) on the 

 one side, and the great masses of contorted secondary rocks of Altorf 

 on the other, the valley extending from Brunnen to Sewen and Schwyz 

 is another of these troughs, the sides of which are composed of the 

 secondary limestone, dipping, on both banks of the river, under the 

 nummulitic and shelly deposits. On the northern side the sym- 

 metrical order of succession is very clear, as exhibited in this dia- 

 gram (fig. 11). Commencing the ascending section on the edge of 



Fig. 11. 

 Relations of Cretaceous and Nummulitic rocks at Sewen. 



Dip 25°. 



N.N.W. 



E-ne. {J; Z^J^- 



: g. Flysch (denuded). 



" ic rocks. 



Cretaceous. 



d e b 



re. Passage beds obscured. 



d. Sewer-kalk (Inoceramus limestone). 



c. Gault and upper greensand. 



b. Upper Neocomian limestone. | ^ greensand. 



La. Lower Neocomian. J ° 



the lake of Lowerz to the north of Sewen, the dark-coloured lower 

 neocomian limestone and shale («) is overlaid by the light-coloured, 

 crystalline, thick-bedded upper neocomian limestone (6), in which 

 we detected not only numerous sections of the Caprotina ammonia, 

 but also Hippurites Blumenbachiiy with corals and Echini. Imme- 

 diately above these is a narrow depression (c), in which are softer 

 beds, the equivalents of the gault and upper greensand, with small 

 ammonites and other fossils*. 



The next mass which succeeds is the Sewen limestone of the Swiss 

 geologists. This sewer-kalk (d) thus resting on upper secondary 



is of paramount importance is, that the following species occur in the south of 

 France, the Pyrenees and the Alps, thus identifying the group : — 



1. Nummulites millecaput, Boubee = N. polygyratus, Desk. 



planospira, Boubee = N. assilinoides, Rilt. 



Biaritzana, D'Archiac = N. atacica, Leym., N. acuta, Sow., and 



N. regularis, Rut. 



globosa, Riit. (var.5iflri7zawa,D'Arch.) = N. obtusa,i/o/y et Leym. 



rotularis, Desh. = N. globulus, Leym. 



placentula, Desh. =N. intermedia, D^Arch, 



IcBvigata (Lam.). 



2. 

 3. 



4. 

 5. 

 6. 



7. 



1. Orbitolites discus, Riit. 



2. patellaris, Briinner. 



3. stellaris, Briinner =Calcarina stellaria, D'Arch. 



Operculina near to 0. ammonea, Leym. 



* Several fossils of the greensand have been found here by Studer and Escher. 

 The latter geologist was we believe the first to name the overlying limestone Sewer- 

 kalk, and to show how a similar limestone occupied a similar place in the canton 

 of Appenzell, and on the lake of Wallenstadt. 



