358 Professor Sedgwick and Mr. Murchison on the 



(). Alternations of blue and grey marls. Both this and the preceding subdivision are of 

 considerable thickness. 



c. Alternations of yellow, micaceous sand and sandy marls. 



5. Greenish grey, micaceous, thin-bedded sandstone. The finer varieties are largely quarried 

 for grindstones ; of the coarser varieties, some resemble the Pennant grit of the Bristol coal, 

 field, and others pass into a fine conglomerate with quartz pebbles. This group is of a thickness 

 amounting to several hundred feet, and portions of it are well exposed near the top of the Res- 

 senberg. 



6. Partly on the same parallel with the preceding group, but apparently rising still higher in the 

 series, is a system of beds forming the highest ridges of the Horn, Their aggregate thickness is 

 not less than five hundred feet ; and they are chiefly composed of red, slaty, micaceous sandstone 

 (variegated with green and grey blotches, and so far resembling new red sandstone) alternating 

 with greenish and reddish arenaceous marls, and without organic remains. 



Such are the groups composing the great overlying deposits of Gosau; and 

 we believe we may assert with the greatest confidence, that in the neighbour- 

 ing mountains no strata are found of a higher geological order, or which have 

 the semblance of passing over them. They seem to have been deposited in 

 a deep bay of the Alpine limestone, and to have originated in the degradation 

 of the surrounding rocks : and if we suppose that the strata of the Horn were 

 in part regenerated from the new red sandstone of Abtenau, and the strata of 

 the Ressenberg from the green-sand on the west side of Blankenstein, we 

 shall have a probable explanation of some of the appearances put on by the 

 preceding groups. 



If we inquire respecting the age of these overlying deposits, the question 

 can only be answered by appealing to their structure, their relations to the 

 older strata, and their fossils ; and arguments derived from these sources may 

 be strengthened by the evidence of analogous sections in other parts of the 

 chain. Now, there is nothing in the structure of the Gosau series to prove 

 that the whole of it is older than the chalk ; and by the evidence of actual 

 sections it appears to be superior to the secondary hippurite-rock, as well as 

 to a part of the green-sand series of Blankenstein. It seems, therefore, to be 

 precisely on the same parallel with a portion of the beds on the north side 

 of the Untersberg section* above described. 



Again, the upper shell-tnarls of Gosau not only contain innumerable fossils, 

 especially univalves, in their mode of preservation as well as in their other 

 characters, resembling those of known tertiary deposits ; but several of them 

 are also identical with species, found in the highest shell-marls of the Unters- 

 berg section. Every inference derived from that section might therefore, we 



* Plate XXXVI. fig. 9. 



