318 Professor Sedgwick and Mr. Murchison on the 



admitted with modifications. The upper limits of the system (partly in conse- 

 quence of the enormous derangements of the Alps) are often almost impossible 

 to determine. On the north flank of the Untersberg- it ends, however, natu- 

 rally with the beds of the hippurite-rock*. At the Wand, Windishgarsten, 

 and in the valley of Gosau, there are also bosses of this rock most intimately 

 associated with, and apparently forming a part of, tlie upper Alpine limestone 

 series, and dipping under certain deposits which we consider of the age of the 

 green-sand. Hence we are disposed to separate the hippurite-rock from the 

 green-sand, and to place it in the highest part of the younger Alpine limestone. 



7. Alternations of Limestone, Calcareous Grit, Sandstone, Marl, &;c.; with 

 numerous Impressions of Fucoid Bodies, and sometimes with Fossils of the 

 age of the Green-sand ami Chalk. 



There are many portions of the Alps, where we believe no mineralogical 

 separation can be established between the lower part of this, and the higher 

 part of the preceding subdivision : and as the hippurite-rock is by no means 

 continuous, being only found here and there in unconnected masses, it is ob- 

 vious that the base of the system of beds, we are describing, must be very ill 

 defined. It was this difficulty which prevented us from separating it, in our 

 published "Sketch of the Structure of the Austrian Alps," from the younger 

 Alpine limestone. We however distinctly recognized its existence on the 

 outskirts of the Salzburg and Bavarian Alps, and stated — "that it formed 

 a succession of ridges close to the tertiary system — that it was composed of 

 alternations of limestone, sandstone, and shale; and being more thin-bedded 

 than the older parts of the chain, had been exposed to extraordinary breaks 

 and contortions ; sometimes dipping towards the mineralogical axis, and 

 sometimes from it ; in one place being vertical, and in another twisted into 

 saddle-shaped masses, and being in some instances absolutely inverted." 

 We further stated — "that this series appears to be greatly expanded near the 

 eastern termination of the Alps — that from the outskirts of the calcareous 

 zone near Reichenhall to the valley of the Rhine, it forms, in the position 

 pointed out, a nearly continuous succession of ridges, easily distinguished from 

 the inner portions of the chain — that in some parts of the series the beds 

 of limestone almost disappear, in which case it passes into a formation of 

 sandstone and shale, not to be separated, without the help of fossils, from the 

 superior tertiary groups — that in other places, lower in the system, the calca- 



* Plate XXXVI. fig. 9. 



