166 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [DcC. 13, 



once cominced that they had been derived from a band of true mu- 

 schelkalk. As the fossils were procured from the band of limestone 

 and shale which surmounts the red sandstone of the plateau upon 

 which we stood, we had therefore already before us two members of 

 the trias. In these valleys the muschelkalk is, however, not only 

 based on red sandstone, but is associated with, and surmounted by red 

 marls representing the Keuper, as seen in the face of the Mittag's 

 Kogel and along various parts of the Schlerns and the Seisser-Alp, 

 and near St. Ulrich in the Grodner-thal, where the whole of the trias 

 is further overlaid by other limestones chiefly Jurassic. 



In proceeding from the Grodner-thal to Colfosco, by St. Christina 

 through the pass of S*^ Maria, the geologist cannot avoid being 

 struck with the grand pyramidal and towering peaks of fantastic 

 shape which the dolomite there assumes in the Lang-Kogel and other 

 mountains*. The great vertical fissures and joints which traverse 

 that rock must not, however, be confounded with the lines of true 

 bedding, which are often more or less horizontal and undulating only, 

 and which, though with difficulty observed by an unpractised geo- 

 logical eye, were visibly delineated before us by wreaths of snow 

 which fell during an autumnal storm on the peaks and escarpments 

 around St. Cassian. The pass of Colfosco, which shows clear 

 sections of muschelkalk on the west, is further remarkable in af- 

 fording fine examples of buttresses of black porphyry (melaphyre), 

 which in one situation, west of Colfosco, is observable in absolute 

 contact with highly dislocated, amorphous, pure white dolomite. I 

 presume that some of this dolomite is of the age of the muschelkalk, 

 because it is associated with certain beds of triassic grit called by M. 

 Emmerich " Halobian sandstein." In descending the valley from 

 St. Cassian by Stern and the Abtey-thal or to the north f, the trias 



anseris since M. Emmerich's visit. The Ammonites Johannis Austrice (Von Hauer) 

 from the lower limestones of Halstadt has also proved to be one of the fossils of this 

 deposit in the Tyrol. 



* The peaks on the south side of this pass are termed Pissada Spitz, Masons 

 Spitz, &c. 



t In his work entitled 'Uebersicht liber die geognostischen Verhaltnisse Siid- 

 tyrols, 1846,' Dr. H. Emmerich distinguishes the following Neptunian deposits 

 in ascending order in this region: — 1. Red sandstone. 2. Posidonia limestone, 

 which he considers the same stratum that contains the Trigonia vulgaris, Tere- 

 braiula trigonella, Gervillia sociaUs and Encrinites liliformis at Recoaro, and 

 is the true muschelkalk. 3. Hornstein-fiihrender kalk, a small and local deposit 

 observed by M. Fuchs. 4. Halobian strata (black sandstone and calcareous 

 schist). This rock (which has been termed grauwacke) is the lias of Klipstein, 

 the ^Yengen deposit of W'^issman, and the dolerite sandstone of Fuchs. 5. 

 St. Cassian beds usually united with the Halobian sandstone. 6. Upper lime- 

 stone with corals and brachiopods, in which, according to M. Fuchs, the fossils 

 of St. Cassian occur at Sotto di Sasso, about 8000 English feet above the sea. 

 Above all these come the Jurassic dolomites. As to the Halobian sandstone, so 

 called from the occurrence of the genus Halobia, it appeared to me to be a rock 

 formed either during submarine volcanic action or out of the detritus of a plutonic 

 mass. It is evidently a local deposit, of which there are no traces near Recoaro 

 and Schio, where it is doubtless represented by other sandstones. The inter- 

 mixture of fossils under the head of " St. Cassian " is accounted for by the fact, 

 that they are collected in the rivulets which descend through Jurassic as well as 

 triassic deposits. 



