1848. J MURCHISON ON THE STRUCTURE OT THE ALPS. 



197 



111 the lower mass, composed of a greenish limestone (/')» nothing 

 but riummulites are visible, chiefly the N. millecaput (Boubee) ; then 

 come greyish blue bands {f^) with other species of nummulites ; next 

 a considerable thickness of marls, sands, &c. (flysch), surmounted by 

 strong reddish and greyish nummulitic limestones (/^). In short, 

 from the bottom to the top of the nummulitic portion of the series, 

 there were intercalations of strata having all the characters of flysch. 

 The great overlying mass {g), however, has been alone styled such by 

 Swiss geologists, and it here spreads in vast thickness over the adja- 

 cent mountains. 



N.N.W. 



Fig. 13. 



S.S.E. 



Schwendberg. 



m m Fault. (/I) (/2) 



m. Upper molasse and nagelflue. 

 P ( g. Flysch. 



ocene. ^ ^ Nummulite limestone alternating with flysch. 



In ascending the little valley of the Sihl from Einsiedeln the same 

 relations of ridges of nummulitic limestones and flysch are still more 

 clearly exposed to the east and west of the village of Gros, where they 

 have also a dip S.S.E. The Sattel mountain on the east side of this 

 valley exposes on its flanks three or four prominent bands of the num- 

 mulitic rock, all dipping to the S.S.E., separated from each other as 

 well as overlaid by considerable thicknesses of flysch (i. e. of sand- 

 stone, limestone, shale, and schist). 



The lower nummulitic limestones visible are dark grey, reddish, 

 and greenish grained, in which occur the large echinidse of Kressenberg, 

 together with ostreae, small nummulites, and large orbitolites. Then 

 intervenes a great mass of shale and sandstone, followed by a second 

 nummulitic limestone and another zone of flysch, and that again by 

 a third nummulitic limestone. In this last-mentioned mass I was 

 much struck with the strong coincidences between some of the coarser 

 nummulitic limestones and the limestone of the so-called " flysch " 

 of many parts of the Alps. They were, in fact, precisely the same 

 thin-bedded, dark grey, sandy limestones mth white veins, and occa- 

 sionally with so many grains of green earth as to become a green cal- 

 careous grit ; the only difference being that the flysch was void of the 

 nummulites and fossils which distinguish the other. These strata, 

 covered by thick beds of grey limestone, pass upwards through shale 

 into fine micaceous flaggy grey sandstone, and thence up into the 

 great series of the so-called *' flysch." A similar intercalation and 

 association is indeed quite as instructively seen just above the village 

 of Gros on the west side of the valley. 



The chief fossils of the nummulitic bands of this district are the 

 Nummulites planospira (Boub.) or assilinoides (Riitt.) ; N. mille- 

 caput ox poly gy rata (Desh.) ; N. Biaritzana (D'Arch.) or regvloris 

 (Riitt.) ; Operculina, apparently a large new species ; Orbitolites 

 discus, and O. parmula ; Pectens, large Ostrese, and some few uni- 



