204 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [DeC. 13, 



known to be neocomian or lower green sand, was wholly omitted ; for, 

 as before said, the neocomian fossils were then miknown, and these 

 rocks were considered to be of jm-assic age. On the other hand, the 

 transition upwards from the equivalent of the chalk into the num- 

 mulitic grit, and thence into the flysch as an overlying mass, was 

 imperfectly explained. In short, having returned to Sonthofen and 

 the Griinten after an interval of eighteen years, and immediately 

 after I had made a consecutive series of sections in strata of this age 

 throughout the Savoy and Swiss Alps, I looked at the masses with a 

 different eye to that with which I viewed them when the only Alpine 

 bases known to me were the rock-masses (often inverted) on the north 

 flank of the Austrian Alps. Even formerly, however, when treating 

 of the flysch with fucoids of this valley of Sonthofen, Prof. Sedgwick 

 and myself offered our sketch as a provisional arrangement only ; 

 stating that a more minute acquaintance v^th the fossil history of the 

 Alps might hereafter lead geologists to a better-defined subdivision of 

 these groups. Profiting, therefore, by the increase of this very fossil 

 knowledge and by a study of the best types in other parts of the chain, 

 and correcting my former views, I now offer sections which I consider 

 to be as clear, copious and instructive, in explaining the succession 

 from the cretaceous to the nummulitic rocks, as any with which I am 

 acquainted. 



The peaked and remarkable calcareous mountain called the Griinten 

 (5923 French feet high), which stands out boldly between Immen- 

 stadt and Sonthofen, and there forms the eastern side of the valley 

 of the Iller, has a general direction from N.E. to S.W. This direc- 

 tion, oblique to that of the chain which trends from W.N.W. to 

 E.N.E,, is connected mth dislocations which affect all this tract. On 

 the north-west face, where the mountain is washed by the Iller, it 

 throws out a spur above the village of Wagneritz or towards Immen- 

 stadt ; to the north it abuts against a mass of tertiary molasse ; on 

 the south-east it is divided into several jagged peaks, the precipitous 

 walls of which preserve a parallelism to the main ridge of summits ; 

 whilst on the south-west, or towards Sonthofen and the upper valley 

 of the Iller, round-shaped buttresses diminishing in height expose 

 an excentric arrangement of strata in ascending order. In a word, 

 the general escarpment of the mountain is to the north-west and 

 north-east, and the prevailing dips of the strata to the south-east and 

 south-west. The best general section may be described as that 

 which exposes an ascending order from the elevated escarpment near 

 Rettenberg on the north-east, to the plain of Sonthofen beyond the 

 village of Burgberg on the south-west. As in proceeding upon this 

 ascending section the strata towards the south-west are found to 

 mantle roimd and overlap the chief nucleus, it follows that lines drawn 

 either to the south or west of the sectional line will exhibit similar 

 successions. Thus, on the south-eastern face of the Griinten, vertical 

 walls of jagged limestone, which diminish in height from the summits 

 of the mountain to the valley of the Starzlach, expose precisely the 

 same ascending order of strata as that which is seen in the masses 

 that fold over at less high angles towards Burgberg and Sonthofen. 



