1848.] MURCHISON ON THE STRUCTURE OF THE ALPS. 163 



ritic schist, is capped on the summit by dark grey, white-veined, 

 fossiliferous limestone, on the surfaces of which many corals weather 

 out. These corals are, Gorgonia infundibiiliformis, Stromatopora 

 concentrica, Cyathophyllutn explanatvjn, C. turbinatufn, C. hexa- 

 gojiuniy C. ccespitosuniy Astrcea porosa (Goldf,), Ileliopora inter- 

 stincta (Bronn), Favosites polymorpha (var. ramosa of the Devo- 

 nian rocks), F. spongites 1 &c. As most of these polypifers range 

 from the Upper Silurian into the Devonian, it might be difficult to 

 class the limestones of Plautsch by reference to them only. The 

 rock also contains, however, Pecten grandcevus (Goldf.), Cyatho- 

 crinites pinnatus (Goldf.), Inoceramiis inversus (Miinster), Ortho- 

 ceras regularise and Goniatites. We also detected a very striking 

 large bivalve, which is not only seen in the slabs of the pavement 

 of Gratz, but which we also found on the summit of the Plautsch, 

 and which we had at first sight believed to be a Strigocephalus. 

 A better specimen, however, led us to think it might prove to be 

 a Pentamerus not remote from the P. Knightii. Until, therefore, 

 more clear specific forms be found and examined, it is not possible 

 at once to say whether the palaeozoic limestone of Gratz be Lower 

 Devonian or Upper Silurian. In extending researches from that im- 

 mediate district to the surrounding country, in which M. Rosthorn 

 has, I am told, already made discoveries which will soon be com- 

 municated to the public, Silurian fossils like those of the tract south 

 of Werfen may also be detected ; and as the presence of carbonife- 

 rous Producti has long been known near Bleiberg in the Carinthian 

 Alps*, we shall then have the exhibition at intervals along both 

 sides of the chief watershed of the Eastern x\lps of sufficient reliquiae 

 of the palaeozoic deposits to convince us of the former existence of 

 considerable masses of sediment of that age. In the meantime, we 

 have ample data to affirm, that large portions of the tract, coloured 

 purple to indicate transition rocks on the map of my coadjutor and 

 self, are occupied by rocks of true palaeozoic age, which in many parts 

 have passed into a crystalline state. 



When, however, the geologist follows these palaeozoic rocks upon 

 their strike to the W.S.W., he perceives that the action of metamor- 

 phism has been much more developed in them. Already to the west 

 of the Gastein Alps and the Grosse Glockner, the masses lying 

 between the granitic or gneissose centre and the flanking walls of 

 secondary limestone are found to be chlorite, talc and mica schists, 

 in none of which have any traces of fossils been yet detected. In 

 travelling in 1847 through portions of the mineral axis both to the 

 east and west of the meridian of Innspruck, in company with M. 

 Leopold von Buch and M. E. de Verneuil, I was forcibly struck with 

 their great change in mineral succession, as compared with the more 

 eastern range of the same masses ; for chlorite and mica schists, 

 assuming in parts almost the characters of gneiss, range up to the 

 secondary limestones with scarcely any place for intermediate strata. 



* A collection of the Bleiberg fossils having been shown to M. de Verneuil and 

 myself at Vienna in 1847, we recognized therein not less than eight or ten s])ecics 

 as belonging to the true carboniferous system of the palaeozoic deposits. 



